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SUSTAINABILITY OF THE KARST ENVIRONMENT DINARIC KARST AND OTHER KARST REGIONS
International Interdisciplinary Scientific Conference (Plitvice Lakes, Croatia, 23-26 September 2009)
Convened and Organised by:
Centre for Karst (Gospi, Croatia) International Scientific Committee
Ognjen Bonacci (Croatia), Chairman Franci Gabrovšek (Slovenia)
Mladen Jurai (Croatia) Božidar Biondi (Croatia) Wolfgang Dreybrodt (Germany) Arthur Palmer (USA)
Derek C. Ford (Canada) David Culver (USA) Andrej Mihevc (Slovenia) Jacques Mudry (France) Daoxian Yuan (China)
Nico Goldscheider (Switzerland, Germany) Zoran Stevanovi (Serbia)
Mario Parise (Italy) Hans Zojer (Austria)
Elery Hamilton - Smith (Australia) Neven Kreši (USA)
Bartolomé Andreo (Spain) Local Organizing Committee
Jadranka Pejnovi, Chair Željko Župan, Secretary Ivo Lui
Neven Boi Aleksandar Luki Ljudevit Tropan Dubravka Kljajo Krešimir ulinovi Ivica Tomljenovi
Foreword
The objective of the international interdisciplinary scientific conference “Sustainability of the karst environment - Dinaric karst and other karst regions”, organized by Centre for Karst, Gospi, Croatia, was to give a theoretical and practical contribution to the concept of sustainable development in karst regions, with a special emphasis on the experiences achieved in the Dinaric karst region. The exchange of information and findings obtained in other karst regions worldwide allows for an integral approach to this complex issue, and thereby contribute towards finding reliable solutions. The basic objective of the conference was to apply an interdisciplinary approach to scientifically assess the issues of sustainable development of all forms of karst.
The issue was approached from different perspectives, from those of a technical and biological nature, to those addressing the social aspects of environmental issues and life on the karst. The conference itself was held at the Plitvice Lakes (World Heritage Site), one of the most fascinating phenomena on Earth. During the conference, one half-day excursion was organized to visit National Park Plitvice Lakes. Following the conference, an excursion was organised to visit several other significant phenomena of the Dinaric karst in Croatia.
Conference themes were:
- Geological aspects
- Geomorphological aspects
- Hydrological and hydrogeological aspects - Coastal and submerged karst
- Biological and ecological aspects of karst - Anthropogenic impacts and protecting karst
- Sociological, demographic and social aspects of karst
- Dinaric karst and other karst regions (China, Alpine, Caribbean karst, etc.)
The publication will serve as a contribution to the VIIth Phase of the International Hydrological Programme (IHP 2008-2013) of UNESCO, which has endeavoured to address demands arising from a rapidly changing world.
Chairman of Scientific Committee Ognjen Bonacci
International Interdisciplinary Scientific Conference SUSTAINABILITY OF THE KARST ENVIRONMENT
DINARIC KARST AND OTHER KARST REGIONS (Plitvice Lakes, Croatia, 23-26 September 2009)
TABLE OF CONTENTS
International scientific and local organising committees ………...
3
Foreword ...4
Table of contents (authors in alphabetical order) ………..………
5
BONACCI Ognjen
Sinking, losing and underground karst streamflows ………..……9
BORDA Daniela, RACOVI Gheorghe, NSTASE-BUCUR Ruxandra, CIUBOTRESCU Christian
Ecological reconstruction of bat cave Roost in western Carpathians …...17
BRINKMANN Robert
Karst and sustainability in Florida, U.S.A. ………..…...25
DELLE ROSE Marco, PARISEMario
Water management in the karst of Apulia, southern Italy ………..….33
DÖRFLIGER Nathalie, FLEURY Perrine, BAKALOWICZ Michel , EL HAJJ Hahmad, AL CHARIDEH Abdoul, EKMEKCI Mehmet
Specificities of coastal karst aquifers with the hydrogeological
characterisation of submarine springs – overview of various examples in the Mediterranean basin ………..…41
DÖRFLIGERNathalie, PLAGNESValérie, KAVOURI Konstantina
PaPRIKa a multicriteria vulnerability method as a tool for sustainable management of karst aquifers - Example of application on a test site in SW France ……….…49
EFTIMI Romeo
Investigation about recharge sources of Bistrica karst spring, the biggest spring of Albania, by means of environmental hydrochemical
and isotope tracers ………....57
GANOULIS Jacques, AURELI Alice, KUKURI Neno
Importance of transboundary karst aquifer resources in South Eastern Europe (SEE) ………....67
GUO FANG Jiang Guanghui
The resources, environment and development in Fengshan Geopark
karst area ………...75
HUBINGER Bernhard , REHRL Christoph, BIRK Steffen
Linking generic models to site-related models of conduit evolution ………83
JAMES Julia M., SPATE Andy
Sustainability in a karst - the Bungonia Caves, New South Wales,
Australia ……….…...91
KATSANOU Konstantina, NIKOLAOUEuaggelos, SIAVALAS George, ZAGANA Eleni, LAMBRAKIS Nikolaos
Hydrogeological conditions and water quality of the karstified
formations of Louros basin, Epirus, Greece ………...97
KNEZ Martin, SLABE Tadej
Karstology and motorway construction ……….…..107
KNEZ Martin, SLABE Tadej
Shilin - lithological characteristics, form and rock relief of the Lunan
Stone Forests (South China karst) ………115
KOVAI Gregor, PETRI Metka
Contribution of time series analysis to the study of the Malenšica
karst spring, Slovenia ……….…123
MALEKOVI Sanja, TIŠMA Sanja , FARKAŠ Anamarija
Capacity for managing local development in karst areas ……….…..129
MUDARRA Matías, ANDREO Bartolomé
Hydrogeological functioning of the karst aquifer drained by Yedra Spring (Southern Spain) from hydrochemical components and organic natural
tracers ………...137
NAUGHTON Owen, JOHNSTON Paul, GILL Laurence
The hydrology of turloughs as groundwater dependent terrestrial
ecosystems ………...147
PARISE Mario
Hazards in karst ……….155
PERNE Matija
Modelling of rillenkarren formation ………163
RUBINICJosip, KATALINICAna, SVONJAMirjana, GABRIC
Ivana,
BUSELIC Gordana, CUZE Maja, HORVATBojanaSalinization of the Vrana Lake in Dalmatia within the context of
anthropogenic influences and climate changes (situation in 2008) ………171
TERZI Josip, PAVII Ante, MARKOVI Tamara, LUKA REBERSKI Jasmina
Protection of the Miljacka karst spring: an underground connection
between the rivers Zrmanja and Krka ………179
9
Sinking, losing and underground karst streamflows
Ognjen BONACCI
Faculty of Civil Engineering and Architecture, Split University, 21000 Split, Matice hrvatske 15, Croatia, e-mail: [email protected]
Abstract: Sinking, losing and underground streamflows are typical and relatively frequent karst phenomena. A sinking surface streamflow can be defined as a surface river or stream flowing onto or over karst and which then disappears completely underground through a swallow hole and which may or may not rise again and flow as a resurgent surface river or stream. A losing streamflow can be defined as an open stream or river that loses water as it flows downstream. The level of water in a losing stream is above the water table: in comparison, the level of water in a gaining stream is below the water table. In a losing stream water infiltrates underground, because the water table is below the bottom of the stream channel. Underground or subterranean streamflows are subsurface karst passages with the main characteristics of open rivers or streams.
In underground streamflows water flows through caves, caverns, karst conduits and large galleries in karst underground. The paper treats some conceptual aspects of sinking, losing and underground streamflows. Some cases of the special hydrological and hydrogeological behaviour of karst sinking, losing and underground streamflows are explained.
Keywords: karst, sinking, losing, underground streamflow
1 Introduction
Karst is defined as a terrain, generally underlain by limestone or dolomite, in which the topography is chiefly formed by the dissolving of rock, and which is characterised by sinkholes, sinking streams, closed depressions, subterranean drainage and caves (Field 2002).
A wide range of closed surface depressions, a well-developed underground drainage system, and strong interaction the between circulation of surface water and groundwater typify karst.
Due to very high infiltration rates, especially in bare karst, overland and surface flow is rare in comparison with non-karst terrains.
Carbonate rocks are more soluble than many other rocks. They are subject to a number of geomorphological processes. The processes involved in the weathering and erosion of carbonate rocks are many and diverse. The varied and often spectacular surface landforms are merely a guide to the presence of unpredictable conduits, fissures and cavities beneath the ground. But at the same time these subsurface features can occur even where surface karstic landforms are completely absent. Diversity is considered the main feature of karstic systems, which are known to change over time and in space so that an investigation of each system on its own is required.
Interactions between the surface and subsurface in karst are very strong (Bonacci 1987).
Groundwater and surface water are hydraulically connected through numerous karst features that facilitate the exchange of water between the surface and subsurface (Katz et al 1997).
High and fast oscillations of groundwater levels in karst control the hydrogeological and hydrological regimes of influent and underground streams. An important issue in studying these streams is that subsurface water is highly heterogeneous in terms of the location of conduits, the location of vertically moving water, and flow velocities. Due to the previously mentioned reasons, the occurrence of losing, sinking and underground streamflows is more the rule than an exception.
10
A great problem regarding the explanation of the hydrological and hydrogeological behavior of such streamflows is connected with the particularities of karst underground features and especially with karst aquifers. Karst aquifers are some of the most complex and difficult systems to decipher. The highly heterogeneous nature of karst aquifers leads to an inability to predict groundwater flow direction and travel times. The circulation of groundwater in karst aquifers is quite different from water circulation in other non-karstic type aquifers. The hydraulic permeability of karst aquifers is essentially created by flowing water and has an anisotropic character.
In karst terrains groundwater and surface water constitute a single dynamic system. Due to this reason one of the almost unavoidable characteristics of open streams, creeks and rivers in karst regions is that they either have partial water loss along their course or completely sink into the underground (Bonacci 1987). Sinking, losing and underground streamflows are more typical, significant and relatively frequent karst phenomena than is reflected in their treatment in the karst literature. A synonym for a sinking and losing stream is an influent stream. Such streams have an integral function in karst hydrology and hydrogeology.
Influent and underground streams develop when they cross soluble rocks along their transfer route to base-level rivers or seas (Ray 2005). Challenges to the investigation of influent and underground streams include the concurrent existence of fast turbulent flow through large karst conduits and slow, diffuse laminar flow through small karst fissures, joints, cracks and bedding plains (the karst matrix). Numerous and extremely varied surface and underground karst forms make unexpected water connections possible in karst medium space, which changes over time. Changes of the underground flow path over the time are caused by:
1) Different recharges from different surface areas, mainly due to the by variable distribution of areal precipitation; 2) Different groundwater levels and their rapid changes in time and space; 3) Anthropogenic influence; and 4) Exogenic and endogenic forces (Bonacci 2004).
The objective of this paper is to discuss the hydrological aspects of losing, sinking and underground streams that are closely connected with the hydrogeological characteristics of the regions through which they circulate. One of the key issues for the better understanding, protection and management of karst systems is the determination of the influent and underground stream catchment area. Due to very special and complex underground and surface karst forms, there are a wide variety of cases of karst sinking, losing and underground streamflows. An attempt at their conceptualisation is provided in the paper. The main issue in the classification of these kinds of karst rivers is that they can be losing, sinking and underground, all at the same time. A description of specific cases of the special hydrological behaviour of sinking, losing and underground streamflows is given.
2 Losing streamflow
A losing streamflow can be defined as an open stream or river that loses water as it flows downstream. A losing streamflow is a surface stream that contributes water to the karst groundwater system in localized areas. It has cracks in its bed that allow water to seep into the groundwater. These losses can be massive in particular river sections, whereas in others they are small and difficult or even impossible to observe without performing especially precise measurements. A direct way surface water becomes groundwater is through the capture of surface streams into subsurface voids through swallets. These features swallow the surface stream and represent a rapid and direct way for groundwater recharge. Losing streams segments are important groundwater recharge zones for underlying karst aquifers.
A losing streamflow is one having a bed that allows water to flow directly into the groundwater system. The water level in a losing stream is higher than the water table, as opposed to the water level in a gaining stream which is lower than the water table. The water than infiltrates underground as the water table is lower than the bottom of the stream channel.
11
Losing streamflows are often used in relation to karst aquifers. Aquifers gain the water lost by the losing stream. Due to very rapid rise and fall of groundwater levels in karst terrains, some losing rivers or their losing stretches can intermittently act as gaining streams.
Figure 1 presents an attempt at the conceptualisation of losing streamflows.
Occasionally, permanent water courses flow beyond the groundwater level, even for 50 m or more. Bonacci (1987, 1999) called these river sections “suspended“ or “perched”. Water infiltrated from these sections can either flow in another catchment or can reappear in the downstream reaches of same river (at the spring B in Figure 1b).
a)
b) B
c) B
river section without losses
river flow direction
sinkhole (swallow hole, ponor)
flow direction of infiltrated water through the large karst conduits in the same river catchment
Legend:
spring
suspended river section
flow direction of infiltrated water through the karst matrix in the same river catchment flow direction of infiltrated water through the large karst conduits in an other river catchment flow direction of infiltrated water through the karst matrix in an other river catchment B spring can be
permanent or intermittent
Figure 1 Conceptualisation of losing streamflows
For example “suspended“ or “perched stretches exist on two neighbouring karst rivers Zrmanja and Krka (Dinaric karst of Croatia). While the Zrmanja River dries out, the Krka River never dries out in these sections. The reason why there are no water losses on the Krka
“suspended” section of the Krka is in the fact that its riverbed is comprised of fine-grained sediments, which make infiltration impossible.
Dye-tracing methods are commonly used to determine groundwater flow paths, relations between surface water and groundwater, and groundwater travel times through the karst underground. It should be stressed that flow paths, connections between certain sinks and springs, very often vary in time and space, mainly due to the varying groundwater conditions in the underground. Complexity of the precise determination of the water losses along open streamflows in karst is discussed by Bonacci (1987).
3 Sinking streamflow
A sinking surface streamflow can be defined as a surface river or stream flowing onto or over karst that then disappears completely underground through a swallow-hole (ponor or sinkhole) and which may or may not rise again and flow as a resurgent surface river or stream.
Infiltration from sinking streams into the karst groundwater system is the most rapid form of recharge for carbonate aquifers (Hess et al 1989).
Sinking streams represent the most direct access to the sensitive and highly vulnerable karst groundwater system. The unique nature of sinking rivers is their development and evolution of conduit flow routes and caves through soluble rocks. The evolution of most of the world’s largest and most significant karst caves and springs are formed as a consequence of large volumes of concentrated recharge from sinking rivers (Ray 2005).
12
Figure 2 presents an attempt at the conceptualisation of sinking streamflows. Sinking stream can reappear at the surface through a typically large karst spring (Figure 2a), though there are some cases when it reappears through many permanent and intermittent karst springs dissipated over a large area.
a)
b)
intermittent (temporary) spring river flow direction
sinkhole (swallow hole, ponor) flow direction of sinking water through large conduits
Legend:
permanent spring
flow direction of sinking water through karst matrix
Figure 2 Conceptualisation of sinking streamflows
Hess et al (1989) explains that the south-Central Kentucky karst aquifer is fed by many sinking streams. Their catchments are made up of an aggregate of many small surface catchments ranging over an area of a few square kilometres. Some of these streams have several surface tributaries, but most of the sinking creeks are short, first order streams.
The Lika and Gacka Rivers (Dinaric karst of Croatia) are typical sinking streamflows.
These rivers are located in the central part of the Dinaric karst region of Croatia (Figure 3) between 44°17’ and 44°58’N and 15°07’ and 15°48’E. Their precise hydrological catchment areas and boundaries are not known (Bonacci and Andri 2008). The Velebit Mountain (max. altitude 1758 m a. s. l.) separates their catchments from the Adriatic Sea.
Water from the both rivers sinks at altitudes between 400 and 450 m a. s. l. and reappears at many permanent and intermittent coastal and submarine karst springs of the Adriatic Sea (Figure 3).
4 Underground streamflow
Underground or subterranean streamflows are subsurface karst passages that have the main characteristics of open rivers or streams. In an underground streamflow, water flows through caves, caverns, karst conduits and large galleries in the karst underground. The karst underground system provides access to fragments of the abandoned conduit system, which have hydraulic geometries comparable, though not identical, to those of surface rivers or streams.
The Port Miou system (Cassis, France) is a two kilometre long submarine gallery that extends in the limestone series of Calanques (Marseille, France). The two largest karst submarine springs, Port Miou and Bestouan, represent the mouths of two underground karst rivers into the Mediterranean Sea. The average discharge of brackish water flowing from the Port Miou spring is between 2 to 5 m3/s (Potié et al. 2005; Cavalera and Gilli 2009). The roof of the entirely submerged Port Miou gallery lies between 10 and 20 m below sea level to about 800 m from the spring exit. It then goes between 10 to 30 m deeper. At about 2200 m from the entrance, the primarily horizontal karst conduit suddenly drops into a deep vertical shaft. Cave divers were able to explore the conduit to a depth of 179 m below sea level. At
13
that depth, the water is still brackish. The system extends further and deeper, however exploration is limited by the present diving technology.
Figure 3 The Lika and Gacka Rivers (Dinaric karst of Croatia), typical sinking streamflows The Cassidaigne canyon cuts the continental shelf where bathymetric studies have shown the presence of dolines. Caves and speleothems have been observed during submarine explorations on the walls of the canyon. Its presence is related to the several stages of the lowering of the Mediterranean Sea during the Messinian salinity crisis. Cavalera and Gilli (2009) suggest that during the important drop of sea level of the Mediterranean, the underground river of Port-Miou, flowed several hundreds meters below its current position, and excavated the canyon. At the end of the Messinian crisis, the system was flooded by sea water. Karst water now flows through an upper gallery, however the presence of a paleo-drain filled by sea water makes deep marine intrusion into the karst system possible. In order to prevent intrusion of sea water, two submarine dams were constructed in the horizontal conduit, about 500 m from the spring exit. However, the issue of contamination with sea water was not resolved by their construction. Cavalera and Gilli (2009) consider that the saline contamination of Port Miou could be carried out by a sea water inflow through a deep karstic conduit connected to the canyon of Cassidaigne.
The Santa Fe River (Florida, USA) flows from an impervious catchment onto karstified Eocene limestones. At the O’Leno Sink, it sinks underground for 5 km before resurfacing at the Santa Fe River Rise. Hisert (1994) conducted a geochemical tracer study to determine which of the numerous karst features occurring between the O’Leno Sink and the Santa Fe River Rise are connected to the underground river. In addition, water temperature measurements were made to distinguish the relative proportions of groundwater and surface water in each water filled karst feature. The results showed that the Santa Fe River Rise is a point of resurgence for a portion of the Santa Fe River flow diverted underground at the O’Leno Sink. The underground river course is singular and sinuous. The flow is conduit and rapid with a velocity of 2.5 km/day (Hisert 1994). The upstream half of the underground river is fairly well delineated, due to the great number of surface sink features. In the downstream
14
section, the underground course is questionable due to the lack of surface karst features that can be used as windows to the karst underground.
Figure 4 presents the map of the Disu underground stream system (Yuan 1991), which has a catchment area of 1004 km2. The system has a total length of 241.1 km, and includes a main conduit that is 57.2 km long and 12 tributaries. The Disu underground system is the longest identified subterranean stream in China. In the upstream section, it is about 100 m in depth, with karst conduits usually in a simple fissure-shape, from several meters to 30 m wide, and ten to tens of meters high. The average hydraulic gradient is about 12%. At the middle and lower reaches, it is 30 to 50 m below the bottom of the valleys. The cross-section of the conduit here varies between 145 and 184 m2, and the average hydraulic gradient is 1%.
Discharges at the exit of the Disu underground river vary from the minimum 4.03 m3/s in dry season to the maximum 544.9 m3/s (Yuan 1991).
Figure 4 The Disu underground stream system in China (Yuan 1991)
5 Discusion
True cases of karst losing, sinking and underground rivers are much more complex than any concept can imagine. In reality, very different combinations exist. Some streams can, at the same time, be losing, sinking and underground.
The Dobra River (Dinaric karst of Croatia) serves as a good example. Figure 5 represents the longitudinal cross-section of the entire Dobra River, divided into three parts.
The first one is a losing and sinking river called Upper Dobra, with a length from the spring to the ula sink-hole of 51.2 km. The second part is an underground karst river flowing from the ula sink-hole to the karst spring zone near the village Gojak. The shortest aerial distance between the ula sink-hole and the Lower Dobra River karst springs zone is 4.6 km. In order to reappear at the karst springs zone, the Lower Dobra River flows through karst caves and conduit system that is 16,296 km long. The longitude of the Lower Dobra River is 52.1 km.
There are huge water losses along some sections of the open watercourse of the Upper Dobra River through small karst sinks located at the bottom of its channel. These have changed over
15
time as a function of the groundwater level. During periods with high groundwater levels losing stretches become gaining stretches.
The importance of sinking, losing and underground streamflows in karst system functioning is very significant. Their hydrological, hydrogeological and other characteristics are extremely complex. Due to these reasons, it is necessary to apply interdisciplinary approaches, methods and concepts in their investigation. It is obvious that efforts aimed at to their better understanding should be intensified.
0.0110.0 11.1110.0 34.8140.0 40.1147.4 48.0175.0 51.7200.0 56.3320.0 60.7322.5 62.6323.0 65.6335.0 350.0 420.0 107.9840.0
94.7
77.9
110.0
175.0 320.0
840.0
"MORAVICE" GAUGING STATION
"LUKE" GAUGING STATION
"HRELJIN" GAUGING STATION
"TURKOVICI" GAUGING STATION
"SV. PETAR" GAUGING STATION
"DANI" GAUGING STATION
"LEŠCE" GAUGING STATION
"STATIVE" GAUGING STATION HEPP GOJAK ULA SINKHOLE
"TROŠMARIJA" GAUGING STATION
RIVER MOUTH RIVER SPRING
ALTITUDE [m a.s.l.]
100 200 300 400 500 600 700 800 900 1000
ALTITUDE [m a.s.l.]
L [km]
0 km 20 km 40 km 60 km 80 km 100 km 107.9km
39.0147.0HEPP LEŠCE
~
Figure 5 Longitudinal cross-section of the Dobra River (Dinaric karst of Croatia)
References
Bonacci O (1987) Karst hydrology with special references to the Dinaric karst. Springer Verlag, Berlin, 184 pp
Bonacci O (1999) Water circulation in karst and determination of catchment areas:
example of the River Zrmanja. Hydrological Sciences Journal 44(3):373-386
Bonacci O (2004) Hazards caused by natural and anthropogenic changes of catchment area in karst. Natural Hazards and Earth System Sciences 4:655-661
Bonacci O, Andri I (2008) Sinking karst rivers hydrology: case of the Lika and Gacka (Croatia). Acta Carsologica 37(2-3):185-196
Cavalera T, Gilli E (2009) The submarine river of Port Miou (France), A karstic system inherited from the Messinian deep stage. Geophysical Research Abstracts Vol. 11, EGU 2009-5591
Katz BG, DeHan RS, Hirten JJ, Catches JS (2007) Interactions between ground water and surface water in the Suwannee river basin, Florida. Journal of the American Resources Association 33(6):1237-1254
Field MS (2002) A lexicon of cave and karst terminology with special reference to environmental karst hydrology. USEPA, Washington, DC, 214 pp
Hess JW, Wells SG, Quinlan JF, White WB (1989) Hydrogeology of the South-Central Kentucky karst. In: WB White, EL White (eds) Karst hydrology concepts from the Mammoth cave area. Van Nostrand Reinhold, New York, pp 15-63
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Hisert RA (1994) A multiple tracer approach to determine the ground water and surface water relationships in the Western Santa Fe River, Columbia County, Florida. Ph.D.
Dissertation, Department of Geology, University of Florida, Gainesville, FL 32601.
Potié L, Ricour J, Tardieu B (2005) Port-Mioux and Bestouan freshwater submarine springs (Cassis-France) investigations and works (1964-1978). Proceedings of International Conference “Water resources & environmental problems in karst”, Belgrade and Kotor, pp 266-274
Ray JA (2005) Sinking streams and losing streams. In: DC Culver, WB White (eds) Encyclopedia of Caves. Elsevier, Amsterdam, pp 509-514
Yuan D (1991) Karst of China. Geological Publishing House, Beijing, 232 pp
17
Ecological reconstruction of bat cave Roost in western Carpathians
Daniela BORDA1, Gheorghe RACOVI1, Ruxandra NSTASE-BUCUR1, Christian CIUBOTRESCU2
1 “Emil Racovitza” Institute of Speleology, Clinicilor St., no 5, 400006 Cluj-Napoca, Romania, e-mail: [email protected]
2 Speleological Association for Environmental Protection and Karst "Sfinx" – Gârda, Romania e-mail: [email protected]
Abstract: The underground environment represents an extreme and, at the same time, fragile environment because of the particularities of biotic and abiotic factors and of its trophic dependence on surface ecosystems. The high constancy of cave factors makes it one of the most vulnerable environments on Earth. Because of the increased human pressure, in the last decades we witnessed a strong degradation of the underground environment in areas exposed to pollution, as a consequence of restraining, retreating or even extinction of specific fauna. In this context we monitor a show cave where the cave electrification and the wood staircase, which facilitated the tourist’s passage in the upper level, were removed. Also, the artificial entrance to the upper level was reversibly obstructed. Our research focused on analyzing the microclimatic conditions, as well as on the airborne microorganisms from the cave, and on the bat dynamics, after the obstruction of the artificial entrance in the upper level of the cave. The results show a direct relation between cave climate, bats, airborne microorganisms, and the cave visitors. From the climatic perspective Poarta lui Ionel Cave is characterized by a permanent bidirectional thermal circulation and the existence of a convection cell exclusively at the level of the lower gallery. The bat monitoring showed that a nursery colony of Miniopterus schreibersii re-inhabited the cave in a very short time after the show paths were removed. The success of the ecological reconstruction was confirmed by the return of the colony next summer. Bats contribute significantly to the generation, spreading and maintaining of a rich and diversified air microflora. Also, the morphology of the cave and its ventilation system contribute to conducting and concentrating airborne microbial communities toward the upper level of the cave. In the evolution of the cave air microflora a seasonal tendency is evident, according to which a quantitative and qualitative maximum is recorded in spring- summer and a minimum in autumn-winter. To conclude, our results reveal important implications for cave and bat management.
Keywords: cave, ecological reconstruction, climate, bats, airborne microorganisms
1 Introduction
The subterranean habitat represents an extreme environment with unique characteristics like its trophic dependence on surface ecosystems, and to the particularities of biotic and abiotic factors (Biswas 2009). The high constancy of these factors makes cave and their associated faunas one of the most vulnerable environments on Earth (Juberthie 2000).
Because of the increased human pressure in the last decades we witnessed a strong degradation of the underground environment followed by the retreating or even extinction of specific fauna (Elliot 2000). Bats are particularly sensible to a persistent human disturbance in maternity sites and hibernacula (Kurta et al. 1993). Disturbances of these roosts are the major cause for the bat depopulation and may induce bats mortality and caves abandonment (Martin et al. 2000). Poarta lui Ionel Cave is an example for the bat depopulation due to improper show exploitation in the last 20 years. A recent effort was realized by the Speleological
18
Association Sfinx Gârda who tried to recover the bat colonies from this cave. The conservation measures, which intended to reduce the human pressure in the bat roost, were accomplished by a climatic study that is still in progress, as well as a mesophilic airborne microorganisms screening. The airborne microbial communities are well represented in the subterranean environment, but not all of them are resident in cave, being carried in from outside by human and animals (Borda and Borda 2006, Borda et al. 2009). Additional work has shown that bats are responsible by an increase of the airborne microorganisms in the cave atmosphere (Borda et al. 2004). Our researches focus on: (i) the analysis of the climate of Poarta lui Ionel Cave after the ecological reconstruction, (ii) determination of the airborne bat-related microorganisms, and (iii) monitoring the seasonal presence of bats in the cave.
2 Materials and methods 2.1 Climatic Data
The temperature and relative humidity were measured by Tinytag Dataloggers Plus 2 (-25 + 85oC and 0 100% RH) registering. The data loggers were set to take the measurements at 1-hour intervals. In order to detect the meroclimatic structure of the cave (Racovi 1984), we established 5 sample sites (samples 1-5), located from entrance to the terminal passage of the cave (Fig. 1). The climatic study is still in progress, the records being carried out for at least one year. Therefore, our results are partial, covering the time period from 15 November 2008 to 11 June 2009.
2.2 Air microflora Samples Collecting
Airborne microorganisms samples were collected by gravitational sedimentation (Koch’s sedimentation method) in two sample sites: in the visiting passage (samples I) from the lower level of cave, and in the passage not open to public access from the upper level of the cave (samples II) (Fig. 1). Investigations were performed seasonally. The specific media were exposed to the cave air for 30 min. After that, the Petri dishes were stored and transported to the laboratory at 50C, where they were incubated in specific conditions.
2.3 Culture Mediums
We used sterile media for the growth of the following groups of air microorganisms:
x Beef-extract agar medium - for the total count of aerobic bacteria growth (TAG);
x Levine medium - for gram-negative bacteria growth (GNB);
x Chapmann medium - for staphylococci growth (SPH);
x Holmes medium - for streptococci growth (STP);
x The Sabouraud medium – for fungi growth (FUN).
The media for the aerobic mesophilic bacteria (TAG, GNB, STP, and SPH) were incubated at 37ºC for 24 hours and the media for fungi was incubated for 3-5 days at 200C, in darkness conditions. The total count of the colony-forming units was calculated using the Omelianski’s formula. The results were expressed per m3 of air (cfu/m3) (Popescu and Borda 2008).
3 Results and discussions 3.1 Cave reconstruction
Poarta lui Ionel Cave located near the village Garda de Sus (Bihorului Mountains, Western Carpathians) is easily accessible, being known by natives from very old times. The cave was first mentioned by J. Vass in 1857 (Bleahu 1976) and described by Jeannel and Racovi (1929). The entrance is represented by a portal impressive by its dimensions (20m
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height and 15m width) open in the background of a rocky amphitheatre. Thus, the name of
“Poarta” (Gate), given to this cave by natives, is very proper. Beyond this portal an active gallery opens, wide of 5-7m and long of 130m that turns twice toward left in right angle (Fig.
1). Except of some fragments on the limestone floor and a big stalagmite flow of 6m height, this sector of the cavity lacks any concretion. In its extremity, on the clayey floor is an excavation in form of a funnel with a diameter of 5m that fills up with water in periods with abundant precipitations. Usually, the subterranean stream appears only at the base of the portal, from a spring situated at the base of the left wall. At high flood the waters appear in the first turn of the gallery among the alluvium accumulated beside the right wall.
Figure 1 Map of Poarta lui Ionel Cave and the samples sites. M I - M II, Airborne Microorganisms sample sites; C 1 – C 5, Climate sample sites
During an international expedition in 1988 an upper level of the cave was discovered, fact that determined the inclusion of the entrance of “Poarta lui Ionel” Cave in a more ample touristic circuit, together with the Scrioara Glacier Cave. The galleries that form the upper level of the cavity are ordered on two levels, inter-connected by a couple of not very deep wells. The terminal part is totally closed by a compact wall of limestone, in which an impenetrable fissure can be seen.
The first arrangements consisted in installing the wood access stairs toward the upper level and digging an opening of about 150/40cm at the base of the stalagmite wall that blocked the access to the new discovered sector. Starting with 1992, the Speleological Association for Environmental Protection and Karst "Sfinx" from Gârda restored the arrangements, and in 2003, together with the mayoralty of Gârda de Sus village, they realised the electric illumination of the cave.
Based on the evidences of chiropterit spots on the ceiling of the cave, and also on the native’s token, the Speleological Association Sfinx Gârda restored the old maternity shelter.
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The ecological reconstruction of the cave started in April 2008 and lasted a few days. The work consisted in the elimination of the cave electrification and of the wood staircase, restricting thus the tourist’s passage to the upper level. Also, the artificial entrance to the upper level was reversibly obstructed with resident stones from the cave and walled in.
3.2 Cave climate
The climatic particularities of the cave are mainly determined by the air currents that move between the exterior and the subterranean void (Racovi 1975). Their origin relies in the thermo-circulation, determined by temperature difference between the subterranean and the surface atmosphere and, implicitly, the air density difference that moves (Andrieux 1970).
Because Poarta lui Ionel Cave has a single communication way with the surface, represented by the big entrance (20m/15m), the air changes with the exterior are permanently bidirectional, with moderate external perturbation. In winter time the cold air enters the cave at the floor level and the warm air from inside out at the ceiling level. In summer time the air thermo- circulation is inverted. Because the lower gallery is huge and slightly ascendant, the air flow is very weak, functioning as cell convection. Besides, the effects of hibernal thermo- circulation upon the subterranean atmosphere materializes by the emergence of an important number of ice formations (stalagmites, stalagmitic domes and parietal crusts), but only in the vicinity of the cave entrance.
The temperature values registered in the lower level of the cave (Fig. 2) show following winter averages (15 November – 31 March): -0.3960C (St. Dev. = 2.346) at the entrance of the cave (sample 1), 1.6510C (St. Dev. = 2.215) at the basal level (sample 2), 3.0190C (St. Dev. = 1.546) in the lake gallery (sample 3).
Lower Level - Sample Site 1
-10. °C -5. °C 0. °C 5. °C 10. °C 15. °C 20. °C
Nov-08 Dec-08 Jan-09 Jan-09 Feb-09 Mar-09 Apr-09 May-09 Jun-09 0.0 % RH 20.0 % RH 40.0 % RH 60.0 % RH 80.0 % RH 100.0 % RH Temperature Humidity
Lower Level - Sample Site 2
-10. °C -5. °C 0. °C 5. °C 10. °C 15. °C 20. °C
Nov-08 Dec-08 Jan-09 Jan-09 Feb-09 Mar-09 Apr-09 May-09 Jun-09 0.0 % RH 20.0 % RH 40.0 % RH 60.0 % RH 80.0 % RH 100.0 % RH Temperature Humidity
Lower Level- Sample Site 3
-10. °C -5. °C 0. °C 5. °C 10. °C 15. °C 20. °C
Nov-08 Dec-08 Jan-09 Jan-09 Feb-09 Mar-09 Apr-09 May-09 Jun-09 0.0 %RH 20.0 %RH 40.0 %RH 60.0 %RH 80.0 %RH 100.0 %RH Temperature Humidity
Figure 2 The air temperature and relative humidity (RH %) trend in the lower part of the Poarta lui Ionel Cave from November 2008 to June 2009
In upper part of the cave, behind the walled gate, the air temperature is constantly higher then in the basal passages (Fig. 3). Theoretically, the upper level can function as a warm air trap and the temperature should rise to about 20°C (i.e. Wonder’s Room from Huda lui Papar Cave, Trascu Mountains). Before digging the artificial opening, the access to the upper level
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was made only through the natural window that has a lower section. Therefore, the existence of considerable temperature differences between the two levels can be excluded. Besides, the natural window that opens close to the ceiling remains inaccessible to any cold air current that move at the level of the floor. As a result, the upper gallery shows a more constant temperature slightly higher than the lower level, 7.6850C (St. Dev. = 0.832) behind of the walled gate (sample 4), and 7.4540C (St. Dev. = 0,123) at the end of the cave (sample 5).
Due to the huge entrance that is the subject to high temperature fluctuations dependent to the external climate and in accordance with the climatic data, the basal level of the cave is represented by a perturbation meroclimate. The relative humidity ranged 67% near the entrance to constantly 100%, above the temporary lake (Fig. 1).
Upper Level - Sample Site 4
-10. °C -5. °C 0. °C 5. °C 10. °C 15. °C 20. °C
Nov-08 Dec-08 Jan-09 Jan-09 Feb-09 Mar-09 Apr-09 May-09 Jun-09 0.0 % RH 20.0 % RH 40.0 % RH 60.0 % RH 80.0 % RH 100.0 % RH Temperature
Humidity Upper Level - Sample Site 5
-10. °C -5. °C 0. °C 5. °C 10. °C 15. °C 20. °C
Nov-08 Dec-08 Jan-09 Jan-09 Feb-09 Mar-09 Apr-09 May-09 Jun-09 0.0 % RH 20.0 % RH 40.0 % RH 60.0 % RH 80.0 % RH 100.0 % RH Temperature Humidity
Figure 3 The air temperature and relative humidity (RH%) trend in the upper part of the Poarta lui Ionel Cave from November 2008 to June 2009
The upper level is represented by a stability meroclimate, where the temperature is constant all year long and the relative humidity was also constantly saturated (Fig.2).
3.2 Bats
Although Jeannel and Racovi (1927) did not cite the bat colony occurrence when they visited the cave, the spots of chiropterit on the ceiling and parietal leaking, as well as the testimony of natives prove that “Poarta lui Ionel” Cave sheltered in the past significant bat nurseries. In the period of tourist management during our research we did not record any bat colonies. We recorded a few specimens of Myotis spp., Rhinolophus spp, Barbastella barbastellus, Plecotus spp. only in the lower level, at the beginning of the winter.
After the pressure induced by tourists was eliminated and the cave was brought back to the natural state, the bat colonies immediately installed in the old summer roost. In May 2008 a nursery colony of Miniopterus schreibersii of more than 150 individuals was found in the upper part of the lower level of the cave (about 20 m high). The bats re-inhabited the cave in a few weeks after the ecological reconstruction of the cave was implemented. The success of the ecological cave reconstruction was proved by the maternity colony of M. schreibersii that returned to the cave in May 2009.
Pursuant to the climatic traits, the lower level of the cave is not suitable for bats hibernation. But in the upper level the climate is more constant, with higher temperatures.
Therefore, Rhinolophidae prefer that part of the cave for the hibernation period. During the winter 2008-2009 in this part of the cave were recorded Rhinolophus ferrumequinum (13 ind.), R. hipposideros (1 ind.), R. euryale (1 ind.), Myotis myotis/M. oxygnathus (2 ind.), Myotis spp.
(1 ind), Miniopterus schreibersi (5 ind). All species encountered in the cave are strictly protected (Annex II, 13/1993 Law), migratory species (Annex II, 13/1998 Law) and also species of European Community interest whose exploitation may be subject to management measures (Annex 3, 57/2007 OU).
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We consider that the main perturbation factor that contributed to bat colonies extinction in the Poarta lui Ionel Cave was represented by human disturbance in the vulnerable periods of their biological cycle. To this, we can add the system of electric illumination of the cave and the gate with vertical bars, placed at the artificially digging opening from the base of the upper level.
3.3 Airborne microorganisms
The results concerning the airborne microorganisms diversity and concentrations in Poarta lui Ionel Cave are showed in Fig. 4. Total aerobic germs showed the highest values, corresponding with the beginning of the bats maternity season. The morphology of the cave imprints a stability climate at this level, with higher temperatures than in the lower level, favourable to the development of a mesophilic air microflora. Besides, the air circulation favours the airborne microorganisms to remain captive in the upper level.
The presence of bats and guano, corroborated with morphological particularities of the cave (Borda et al. 2004) explains the high incidence of the five groups of microorganisms with hygienic significance and the high number of colony forming units in the upper level compared with the lower level. The presence of fungi is less significant, compared with that of other microorganisms, their occurrence being in an increased number in the lower level, close to the entrance. Usually the fungi originate from the exterior (Caumartin 1966, Koilraj et al. 1999), their number decreasing from the entrance to the profound areas of the cave (Borda and Borda 2006).
0 1000 2000 3000 4000 5000 6000 7000 UFC/m3
Autumn Winter
Spring Summer
Airborne Microorganisms in the Upper Level TAG STP SPH GRN FUN
0 1000 2000 3000 4000 5000 6000 7000 UFC/m3
Autumn
Winter
Spring
Summer
Airborne Microorganisms in the Lower Level TAG STP SPH GRN FUN
Figure 4 Seasonal variations of airborne microorganisms in Poarta lui Ionel Cave
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The seasonal tendency of air microflora indicates a maximum of the mesophilic bacteria in the warm season, during the summer for the lower level and during the spring for the upper level. The absence of fungi in the spring can be explained by their biological cycle.
All these data are important for the future cave management plans that should take into account the needs of the bats, the effects of human disturbance upon the bat populations and also the airborne microorganism biohazards.
3 Conclusions
After the ecological reconstruction, the Poarta lui Ionel Cave was re-populated by a maternity colony of Miniopterus schreibersii. The climatic particularities of the cave support the bats colonies. This is characterised by a permanent bidirectional thermo-circulation and by the existence of a cell convection that closes at the extremity of the lower gallery, without affecting the upper level of the cave. Bats significantly contribute to the spreading and maintaining of a rich and diversified air microflora. The morphology and ventilation of the cave contributes to the directing and concentrating the airborne microbial communities toward the upper level. A seasonal tendency of airborne microorganisms is evident, being assured by the temperature of the external environment and by the presence of tourists. Therefore, we consider these investigations relevant for cave conservation and for the protection of various types of bat colonies that inhabit these caves, even in the conditions of tourist exploitation.
Acknowledgments
We thank the staff of the Apuseni Natural Park Administration, who helped us and contributed with logistics in the field. We are particularly thankful to Negrea Avram for field assistance.
This study was supported by The ID_2325 Grant from CNCSIS.
References
Andrieux C (1970) Contribution a l’étude du climat des cavités naturelles des massifs karstiques. II. –Aérodiynamique souterraine. Ann. Spéléol. XXV(2):491-529
Bleahu M, Decu V, Negrea S, Plea C, Povar I, Viehmann I (1976) Caves from Romania, Ed. tiin. Enc. 415 pp
Borda D, Borda C, Tma T (2004) Bats, climat, and air microorganisms in a Romanian Cave. Mammalia 68(4):337-343
Borda C and Borda D (2006) Airborne microorganisms in show caves from Romania.
Trav. Inst. Spéol. “Émile Racovitza” 43-44: 65-74
Borda D, Bucur-Nstase R, Borda C, Gorban I (2009) The assessment of the airborne microorganismes in subterranean environment, Bulletin UASVM, Veterinary Medicine 66 (1) (in press)
Caumartin V (1966) Principes de repartition des associations d’organismes microscopiques en caverns. Bull. Sci. Bourgone 24:39-56
Elliot W R (2000) Conservation of the North American cave and karst biota. In:
Wilkens H, Culver D C, Humphreys W (Eds.) Ecosystems of the World - Subterranean Ecosystems, Elsevier. pp 665-689
Jayant B (2009) The biodiversity of Krem Mawkhyrdop of Meghalaya, India, on the verge of extinction, Current Science 96(7):904-910
Jeannel R, Racovi E G (1927) Enumération des Grottes visitées, 1918-1927 (VII-e série). Archives de Zoologie Expérimentale et Générale 68(2):293-608
Juberthie C (2000) Conservation of subterranean habitats and species. In: Wilkens H, Culver D C, Humphreys W (Eds.) Ecosystems of the World - Subterranean Ecosystems, Elsevier, pp 691-700
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Koilraj A J, Marimuthu G, Natarajan K, Saravanan S, Maran P., Hsu M J (1999) Fungal diversity inside caves of Southern India. Current Science – Bangalore 77(8):1081-1083
Kurta A, King D, Teramino J A, Stribley, J M, Williams K J (1993) Summer roosts of the endangered Indiana bat (Myotis sodalis) on the northern edge of its range. Am Mid Nat, 129:132-138
Martin K V, Puckette W L, Hensley S L, Leslie D M (2000) Internal Cave Gating as a Means of Protecting Cave-Dwelling Bat Populations in Eastern Oklahoma. Proc. Okla. Acad.
Sci. 80:133-137
Popescu S, Borda C (2008) Igiena Animalelor i Protecia Mediului. Lucrri Practice.
Editura Napoca Star Cluj-Napoca, 167 pp
Racovi G (1975) La classification topoclimatique des cavités souterraines. Trav. Inst.
Spéol. „E. Racovitza” 14:197-216.
Racovi G (1984) Sur la structure méroclimatique des cavités souterraines. Theor. Appl.
Karstol. 1:123-130
25
Karst and sustainability in Florida, U.S.A.
Robert BRINKMANN
Karst Research Group, Department of Geography,
University of South Florida, Tampa, FL 33620, USA, e-mail: [email protected]
Abstract: The State of Florida, which consists of one of the most extensive karst regions in the Americas, is also one of the fastest growing regions in the United Starts. The population increases, which are driven by both migrations into Florida from within the United States and from many areas of the world, particularly Latin America, put significant pressure on the karst systems within Florida’s fragile subtropical environment. Within this cultural and environmental context, various stakeholders are attempting to address a variety of sustainability issues unique to Florida’s subtropical environment. It is evident that karst systems impact in some way key sustainability sectors such as water, food and agriculture, building, energy, and greenhouse gas management.
Florida’s karst waters are continually under thread due to over pumping and pollution.
Improvements in the systematic management of water eliminated some of these problems.
Agricultural production in the state often impacts the state’s karst systems through water extraction, irrigation, and associated fertilizer pollution of the aquifer. Local limestone and marine sand is used in the construction of concrete block building materials. Offshore oil and gas reserves, often found in limestone, are not utilized and the state relies on external sources for energy.
Nevertheless, there is a growing interest in developing local policies to address greenhouse gas emissions, some of which involve carbon sequestration within karst systems. A policy review of these five themes reveals that Florida provides strong examples how sustainability can be thematically approached within a subtropical karst environment. The United States Government, until recently, has not provided guidance on a variety of sustainability issues. But at the local level, a number of government and non-government organizations are addressing these important topics.
The development of local approaches to enhancing environmental sustainability in karst environments requires examination of regional environmental settings and how human activity impacts them.
Keywords: karst, sustainability, Florida
1 Introduction
The state of Florida has undergone tremendous population growth in the last 100 years as its population doubles approximately every 20-30 years (U.S. Census 2009). However, it is also one of the most fragile karst systems on the planet with regional interconnected ground water systems, dozens of high-flow springs, hundreds of caves, and unique sinkholes and wetlands (Brinkmann et al. 2007, Brinkmann and Reeder 1994, Fleury, Carson, and Brinkmann 2008, Florea 2006, Scott et al 2004, Screaton et al. 2004, Tiahnsky 1999). The high growth coupled with the natural vulnerability of karst landscapes (North, van Beynen, and Parise 2009), provides challenges for environmental managers. In the last several years, indices that measure community-scale sustainability were developed to benchmark sustainability efforts at the county and local levels in Florida (Florida Green Building Coalition 2009, Myfloridaclimate 2009, Upadhyay 2009). These matrices evolved, in part, due to the complex political landscape of the state that encourages economic development while preserving natural resources. Within this context, the Governor of Florida, Charlie Crist, challenged local governments and state agencies to develop strategies to reduce greenhouse gases and improve the overall environmental sustainability of their organizations
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through Executive Orders 126, 127, and 128 (Crist 2007a-c). Due to this challenge, dozens of communities adopted specific policies to enhance sustainability in their operations. While many of these approaches are still evolving, several strategies directly impact karst systems.
The new policies can be grouped into strategies for water, food, building, energy, and greenhouse gas management.
Prior to discussing each of these in detail, it is worth reviewing the nature of the karst systems in Florida. To many, Florida is a flat, featureless plain. Throughout its approximate 150,000 square kilometers in area, the maximum elevation is 105 meters and the local relief in many portions of the state is difficult to discern. However, upon closer examination, Florida is home to a diverse karst landscape. Its carbonate platform underwent a series of marine transgressive cycles that modified existing carbonate and created new carbonate and sandy marine sediments and rocks. As a result, the state contains older carbonate ridges that were exposed for longer periods than the surrounding lowlands. In addition, in many areas, marine sands blanket the limestone, thereby creating a covered karst landscape. The landforms in the lowlands are what one would expect to see in recently emerged karst plains. Circular dolines dominate the landscape and streams are uncommon. Most of the drainage is to the subsurface were hundreds of kilometers of flooded underground caves are found. In addition, springs are commonly found in these lowland areas. Many form spring runs that lead directly to the coast.
In contrast, the karst landscapes on the older ridgelands are more complex. Here, karst depressions are extensive and their forms are complicated. These uvalas are often sites of air- filled cave entrances.
The karst landscape is continually forming in Florida. It is evident through the composition of spring water exiting karst aquifers that solution of limestone is occurring at a rapid rate (Scott et al. 2004). There are hundreds of homeowners’ insurance claims in the state each year due to sinkhole damage (Eastman et al. 1995). In addition, human activity, such as over pumping of aquifers, enhances depression formation. The karst plain in Florida, due to its active nature is quite vulnerable because of the 18 million residents that live on top of it.
Nevertheless, there are some interesting approaches that have been taken in recent years that improve the overall environmental sustainability in Florida’s karst systems
2 Approaches to environmental sustainability
The approaches to environmental sustainability will be discussed within five major themes: water, food and agriculture, building, energy, and greenhouse gas management.
Certainly there are others that could be explored, such as population sustainability and disaster resilience. Nevertheless, karst systems have the greatest impact within these five sustainability themes in Florida.
2.1 Water
Florida experiences high variation in monthly precipitation. During the summer and early fall, rainfall is quite high due to sea-breeze induced convectional thunderstorms, and occasional tropical storms and hurricanes. Precipitation can exceed several centimeters daily and depressions are filled with storm water runoff via overland flow. Ephemeral rivers begin to flow and the discharge in perennial streams and springs increases. In dry months, many springs and streams either dry out or decrease their discharge significantly. Karst wetlands, lakes, and pond may dry. Within this environment, water managers must provide drinking water to millions of people. Unfortunately, the production of water in Florida in the late 20th century caused a reduction of the regional groundwater table and concomitant drying of wetlands, lakes, and rivers. Collapses of the land surface into underground voids increased.
This occurred largely due to the decision to manage water in the state within local water management districts. Thus, a region like Miami must find water within their local region and
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cannot import it from wetter areas of the state. They must use whatever sources they can within their region. While all efforts are made to protect the environment, withdrawals occur during extreme drought periods in late winter and early spring.
Thus, there have been significant impacts to the karst systems in Miami, Tampa, and Orlando due to ground water withdrawal (Rand 2003). However, this sustainability tenet of
“using local” water supplies has let to innovative approaches to water management. For example, several governments in the Tampa Bay area formed Tampa Bay Water, an organization charged with providing drinking water to the region. Because the region cannot withdraw more from the aquifer without further damaging the karst systems, Tampa Bay Water developed a 25 million gallons of water per day desalination facility and built a 15 billion gallon reservoir that supplements surface and groundwater sources. While one may question the carbon footprint of the desalination plant and reservoir within a sustainability context, there is no doubt that these innovative projects prevented further damage to the region’s karst environment as the region’s water demand increased.
2.2 Food and agriculture
Florida is one of the most productive agricultural states in the U.S (USDA 2008). It is a major beef and dairy producer, although it is probably best known for its citrus groves, strawberry fields, and fresh produce farms. It is also home to niche agricultural markets such as caladium bulbs, orchids, and tropical fish production. Farms and food processing use the greatest amount of water than any sector in Florida (USGS 2009). Water withdrawals in some agricultural areas trigger sinkhole collapses and local well failure (Tehansky 1999). For example, in 1997, strawberry farmers induced sinkholes in rural Polk County Florida when they sprayed millions of liters of water on their crops to prevent them from freezing. Of special concern in the state is nitrogen and other fertilizers and pesticides that enter the groundwater system and rapidly disperse within the interconnected karst aquifers. Nitrogen pollution has steadily increased in springs in the state (Katz 2004, Scott et al. 2004) as a result of increased fertilizer use not only on agricultural lands but also on lawns and golf courses that are ubiquitous on the Florida landscape.
New approaches to organic farming, community sponsored agriculture, and community gardening can reduce the impact in some settings. In the last few years, there has been a rapid increase in these efforts in the state. In the Tampa Bay area, for example, several hydroponics and soil-based community gardens started, several organic farms began operation on the edge of the urbanized area, and there is great interest in local governments in encouraging community sponsored agriculture. In addition, many golf courses are using “green” golf course management protocols that reduce fertilizer runoff and officials are encouraging replacement of lawns with native vegetation and trees. However, Florida’s unique growing season makes it a significant fresh food source for many parts of the world and the impacts of agribusiness cannot be discounted.
These large food-producing organizations are also trying to do their part to enhance the region’s sustainability. For example, many farms are developing drip irrigation or are transforming fields to hydroponic operations. Others are using hi-tech irrigation schemes that reduce their overall groundwater use. In addition, many agricultural fields take the solid wastes from sewage treatment plants in urban areas, thereby reducing their need for fertilizers.
There is also great interest in Florida in developing biodiesel fuels from agricultural crops that need little to no fertilization. The state has invested in research into a variety of crops and there are some biodiesel plants currently in operation. Associated with this is the emerging area of using vegetation in Florida for carbon capture. Large landholders are examining the profitability of transforming pasture or croplands into forested land within the carbon trading market. With the new administration within the executive branch of the U.S. government and
