Changes in land and water use and management

Changes in land and water use and management encompass a wide range of effects, many of which will influence or be influenced by other drivers discussed in this chapter. In the context of ter-restrial ecosystems, such changes have classically been studied and categorized using the concept of “land-use transitions” (e.g. Foley et al., 2005;

Mazoyer and Roudart, 2006; Ruthenberg, 1980).

According to this concept, changes in land use follow a unidirectional pathway of succession from the natural ecosystems of the pre-settle-ment period, through smallholder subsistence agriculture, to landscapes dominated by inten-sive agriculture interspaced with urban, recrea-tional and conservation areas. This classical view broadly reflects the history of land-use changes in many temperate and tropical regions of the world, especially those where forests once dom-inated, with the process being most complete in parts of Europe, temperate Asia and North America. However, changes taking place today in locations where the land-transition trajectory is less complete do not necessarily follow the sequential pattern of past events elsewhere. For example, many of the hundreds of thousands of hectares of forest cleared in various parts of the world each year are incorporated directly into large-scale, commercially oriented, intensive crop or livestock production systems without passing

through a phase of being used by smallholders.

The following paragraphs briefly describe major recent land-use trends in various ecosystems used for food and agriculture.

The world’s total forest area has continued to decline in recent years (FAO, 2018b) (see Section 4.5.5 for further discussion of trends in forest ecosystems). In the tropics and subtropics, the expansion of commercial large-scale agricul-ture accounted for 40 percent of forest loss during the period 2010 to 2015 (FAO, 2016e). Smallholder farming accounted for 33 percent of the loss, urbanization and infrastructure for 10 percent each and mining for 7 percent (ibid.). These patterns, however, vary considerably from region to region.

For example, Hosonuma et al. (2012) estimated that during the period 2000 to 2010 transformation to commercial agriculture accounted for almost 70 percent of forest-area loss in Latin America, compared to about 35 percent in Africa and Asia. In Africa, 40 percent was lost to subsistence farming and up to 10 percent to mining (ibid.).

In recent years, forest loss (mostly native forest) has been partially offset by natural expansion of forest (2.2 million ha/year during the period 2010 to 2015), often onto abandoned agricultural land, notably in Europe and Central America, and by forest plantations (3.1 million ha/year during the period 2010 to 2015), particularly in parts of Asia (FAO, 2016e).

In addition to reductions in the absolute extent of forest area, forest fragmentation is a major threat to biodiversity and ecosystem-service pro-vision (Haddad et al., 2015), as is conversion from natural forests to monoculture forest plantations in some parts of the world (e.g. Ahrends et al., 2015; Edwards et al., 2010; Hosonuma et al., 2012;

Warren-Thomas, Dolman and Edwards, 2015). It has been estimated that 70 percent of the world’s remaining forest area is within 1 km of a forest edge (Haddad et al., 2015). Fragmentation has implications for habitat structure and quality, microclimate, hydrology, and wildlife recoloni-zation and dispersal. It also increases accessibility and thus increases pressure on wild foods and other forms of associated biodiversity.

Land use for livestock production has tradi-tionally involved either integrated crop–livestock systems (see Section 5.5.1) or extensive grass-land-based systems. In places, initially in devel-oped regions such as Europe and North America, but in recent decades increasingly in other regions, mixed production has tended to give way to spe-cialized intensive crop production systems on the one hand and “landless” livestock systems on the other. In the case of grassland production, tradi-tional management systems and practices, notably mobile pastoralism, have declined in many parts of the world (FAO, 2009a, 2015a). Large areas of species-rich grassland have been replaced by croplands or high-yielding single-species grass-lands (see Section 4.5.6). In other cases, changes in management have contributed to grasslands becoming overgrown with shrubs. Extensive com-mercial grassland livestock production has also declined in some places over recent years. For example, expansion of soybean production in South America is taking place on land previously cleared of forest for livestock production (De Sy et al., 2015) – with the soy produced going to feed animals in an increasing number of large-scale intensive landless livestock operations, both in the region and elsewhere (Modernel et al., 2016).

These various changes have been accompanied by an increase in the global population sizes of all major livestock species, although with considera-ble regional variations (FAO, 2015a).

Land-use changes associated with livestock pro-duction threaten biodiversity in various ways. Direct effects include those caused by effluents from land-less production units or other intensive systems escaping into waterbodies and those caused by excessive or badly managed grazing. Indirect effects include those associated with demand for raw materials to produce concentrate feeds (Godde et al., 2018). Livestock production is also one of the main sources of greenhouse-gas emissions, accounting for 14.5 percent of all global emissions by some estimates (Gerber et al., 2013). The loss and degradation of grassland areas around the world has negative implications for many species, including, for example, many birds (see Box 3.3).

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box 3.3

Unsustainably managed production systems are a key threat to bird species BirdLife International classifies the extinction risk of all the

world’s birds for the International Union for Conservation of Nature Red List. Their 2017 assessment concluded that 1 469 species of birds (13 percent of extant species) are globally threatened with extinction (BirdLife International, 2018). While birds provide many ecosystem services to production systems, unsustainable management of these systems has a negative impact on bird populations. As shown in the figure below (on the left) the three most important threats globally (those with the largest number of species facing the highest level of threat) are agriculture, which affects 911 threatened bird species (73 percent), logging and wood harvesting, which affect 669 species (54 percent), and invasive alien species, which affect 422 species (34 percent) (Butchart et al., 2010).

In recent decades, both increases in the extent of cropland (particularly marked in the tropics) and intensification of agriculture have driven the loss of natural habitats and increased threats to birds (BirdLife International, 2013). For example, the European Farmland Bird Index showed a 55 percent decline in common farmland birds between 1980 and 2016, and the downward trend appears to be continuing (see figure below on the right).

Long-term trend data for Europe (1980 to 2016) are based on national breeding-bird surveys in 28 countries collated and synthesized by the Pan-European Common Bird Monitoring Scheme (EBCC, 2017; Gregory et al., 2005, 2008;

Gregory and van Strien, 2010). A large body of research in Europe has attributed the steep decline of farmland birds to a general process of agricultural intensification, which has adversely affected many other taxa in addition to birds (Donald, Green and Heath, 2001; Donald et al., 2006;

Gregory et al., 2005).

Similar trends are seen in the marine environment.

Increased fishing pressure is affecting seabird numbers, especially long-lived species such as albatrosses (Anderson et al., 2011a). At Bird Island (South Georgia), long-term monitoring and demographic studies have revealed steady declines of 2 to 4 percent per year over the last few decades for the wandering albatross (Diomedea exulans), grey-headed albatross (Thalassarche chrysostoma) and black-browed albatross (T. melanophrys) as a result of bycatch from longline fisheries (Croxall et al., 1998; Pardo et al., 2017).

Source: Provided by the Royal Society for the Protection of Birds (RSPB) and BirdLife International.

Human intrusions & disturbanceTransportation & service corridors Fisheries

High/medium impact Low impact Unknown impact Expansion and intensification of agriculture

are the most important of many threats affecting threatened bird species

1980 1985 1990 1995 2000 2005 2010 2015 2020

Population Index (1980 = 100)

All common birds (n = 168 species) Common forest birds (n = 34 species) Common farmland birds (n = 39 species) European Union Wild Bird Index 1980 to 2016

Source: Butchart et al., 2010.

Number of species

Human intrusions & disturbanceTransportation & service corridors Fisheries

High/medium impact Low impact Unknown impact Expansion and intensification of agriculture

are the most important of many threats affecting threatened bird species

1980 1985 1990 1995 2000 2005 2010 2015 2020

Population Index (1980 = 100)

All common birds (n = 168 species) Common forest birds (n = 34 species) Common farmland birds (n = 39 species) European Union Wild Bird Index 1980 to 2016

Source: EBCC/RSPB/BirdLife International/Statistics Netherlands.

Agriculture accounts for the largest share of water withdrawals worldwide (approximately 70 percent of the total), although the proportions taken by industry (approximately 20 percent) and by domestic use (approximately 10 percent) are increasing, as is the share taken by urban areas rel-ative to rural areas (FAO, 2011a). This trend is more pronounced in high- and middle-income countries than in low-income countries, where agricul-tural withdrawals still account for 90 percent of the total. The area equipped for irrigation has more than doubled worldwide over the last five decades, from 139 million ha to 301 million ha (an increase from 10 percent to 20 percent of the total cultivated land area), while water withdrawal for irrigation grew from 1 540 km³ to 2 710 km³ per year over the same period. About 80 percent of this capacity is located in low- to middle-income countries (ibid.). The consequences of irrigation expansion for BFA are variable and context specific.

However, major irrigation infrastructure devel-opments are often associated with the expansion of market-oriented monocultures such as sugar cane or cotton, while the infrastructure associated with irrigation schemes (dams, channels, etc.) can also affect aquatic biodiversity (e.g. Tendall et al., 2014; Verones et al., 2012). Poorly managed irri-gation can result in salinization, the accumulation of water-soluble salts in the soil, which eventually inhibits crop growth. At least a fifth of irrigated land is believed to be salt-affected to some degree (Pitman and Läuchli, 2002), with researchers suggesting that half of all arable land might be affected by 2050 (Butcher et al., 2016).

Wetlands and inland aquatic ecosystems around the world are facing a range of expand-ing demands, includexpand-ing those associated with agriculture, urban development, flood protection, transport and hydropower generation. These are giving rise to a number of serious threats to fresh-water biodiversity, including channelization of watercourses, habitat fragmentation and loss of riparian forests (Angelopoulos, Cowx and Buijse, 2017; Boulton, Ekebom and Gislason, 2016; Carrizo et al., 2017; Speed et al., 2016). The degradation of freshwater ecosystems and loss of their physical

and functional complexity eliminate vital compo-nents of natural flood-control mechanisms, inhibit the recharging of wetlands and destroy and frag-ment habitats that support fisheries (Friberg et al., 2016; Gleick, Singh and Shi, 2001). Weirs, dams and other barriers have interfered with the migratory routes of several fish and river-dolphin species, and reduced connectivity along the length of most large rivers (Addy et al., 2016; Pivari, Pacca and Sebrian, 2017). The loss of riparian forests increases the risk of seasonal flooding and results in the loss of habitat and nursery grounds for fish and other aquatic species (Larsen et al., 2012;

NRC, 2002). In places, however, successful efforts have been made to improve water quality, con-struct fish passages and restore waterway banks to create spawning habitats and increase fish popu-lation sizes (see Section 5.4 for further discussion).

Across production systems, much of the world’s soil is in a degraded and often deteriorating state (FAO and ITPS, 2015). Key threats to soil biodiversity and the capacity of soils to deliver ecosystem services include land-use changes that involve vegetation clearance or the sealing of soils under permanent cover such as concrete, the increasing frequency of forest fires, the spread of inappropriate crop-production practices and over-grazing (Turbé et al., 2010; Orgiazzi et al., eds., 2016). Globally, 33 percent of land is moderately to highly degraded due to erosion, salinization, compaction, acidification and chemical pollution of the soil (FAO and ITPS, 2015). Around a fifth of the Earth’s vegetated surface shows persistent declining trends in productivity, leaving 1.3 billion people living on degrading agricultural land (UNCCD, 2017).

The management of a crop production system involves decisions with regard to (inter alia) what tillage practices will be used, which crop species or varieties will be grown, whether trees or live-stock will be integrated into the system, how crop residues will be managed, what and how external inputs such as fertilizers, herbicides and pesticides will be applied and whether hedges and uncultivated strips will be left around fields or plots. All these decisions will influence the

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characteristics and the diversity of the local soil fauna and flora.

Soil biodiversity is greatly influenced by the quantity and quality of organic matter present in the soil. The biodiversity in overexploited soils is less abundant, dominated by fewer species and characterized by simpler trophic networks (Creamer et al., 2016). Loss of soil organic matter may lead to weaker soil structure, soil sealing, surface crusting and/or compaction, reducing the soil’s capacity to capture and store water, buffer its pH and regulate its salinity.

Declines in the soil’s organic-matter and nutri-ent contnutri-ent are caused by misbalances between inputs and outputs. Inputs are provided by plant litter and by the addition of organic matter and nutrients (e.g. in the form of manure – FAO, 2018f). Losses occur through the decomposition of organic matter and soil erosion. Nutrients can also be lost via leaching, volatilization and removal in harvested products. Soil-nutrient depletion through negative nutrient balances is widespread throughout much of sub-Saharan Africa (Tittonell and Giller, 2013).

Soil biodiversity will generally benefit from management methods that increase the input of organic matter and reduce its loss, for example mulching, manuring and composting. Increasing crop diversity in the form of rotations or intercrop-ping tends to increase soil biodiversity (Tiemann et al., 2015; Zander, Jacobs and Hawkins, 2016).

Tillage generally has a negative effect on soil bio-diversity (e.g. Creamer et al., 2016; Nielsen et al., 2011; Tsiafouli et al., 2015). For further discussion of soil-management practices, and the status and trends of their use, see Section 5.6.3.

Appropriate management of non-cultivated areas within agricultural landscapes is also vital to the supply of many ecosystem services. For example, the health of pollinator populations often depends on the floristic diversity of areas such as field margins (Carvalheiro et al., 2010;

Holland et al., 2015; Ricketts et al., 2008). Further information can again be found in Chapter 5.

The information provided by countries on the effects of changes in land and water use and

man-agement on the supply ecosystem services in dif-ferent production systems is summarized in Table 3.13. In a large majority of cases (i.e. production system by ecosystem service combinations) reports of negative impacts outnumber reports of posi-tive impacts. In some production system categories (livestock grassland-based, livestock landless, nat-urally regenerated forests, rainfed crop and irri-gated crop [non-rice]), this is the case for all eco-system services. Moreover, for several vital ecosys-tem services such as pollination, pest and disease control and water purification, the number of countries reporting negative effects exceeds (or at best equals) the number reporting positive effects across all production systems. However, for all eco-system services there are at least some reports of positive impacts. The most frequently reported positive effects are on the production of oxygen in planted forests and nutrient cycling and soil for-mation and protection services in mixed systems.

The country reports do not always include details of the mechanisms through which land- or water-use changes are giving rise to the reported changes in the supply of ecosystem services. However, some examples are provided.

With regard to aquatic systems for instance, a number of countries stress the negative impact that water-management practices such as the fragmentation of watercourses through the creation of dams, levees, irrigation systems or flood-protection barriers have had on aquatic biodiversity. Several mention that dams and hydroelectric-power schemes have led to declines in river fish stocks. Developments of this kind are reported to have blocked the migration routes of commercially valuable fish species, disturbed the spawning grounds and habitats of a range of aquatic species, contributed to the loss of forest trees near watercourses and negatively affected downstream habitats including those in estuaries and coastal areas. For example, Iraq reports that various large-scale water-diversion projects have degraded the Tigris−Euphrates alluvial saltmarsh and greatly affected land use in this area. It notes also that these effects have been exacerbated by a decrease in rainfall in recent years.

Several countries mention that freshwater or marine biodiversity and related ecosystem services have been negatively affected by wetland con-version for use in crop, livestock or aquaculture production or by the destruction or poor manage-ment of forests. For example, Argentina reports that inappropriate management of forests in the upper stretches of river basins has led to changes in water quality and quantity in low-lying areas and that the conversion of forests into grasslands is affecting the feeding and breeding grounds of fish species targeted by artisanal and sport fisheries.

With regard to the management of marine and coastal ecosystems, the Bahamas reports that fish-eries are being compromised by the creation of navigation channels and the physical destruction of habitats such as coral reefs and mangroves for infrastructure development (docks and piers).

Where wild foods from forests are concerned, the type of land-use change most commonly reported to be having an impact is deforestation, in many cases linked to agricultural expansion and in some to other factors such as urban expansion, mining and infrastructure development.

table 3.13

Reported effects of changes in land and water use and management on the provision of regulating and supporting ecosystem services, by production system

Production systems (PS)

Effects of changes in land and water use management on ecosystem services

Pollination Pest and disease regulation Water purification and waste treatment Natural-hazard regulation Nutrient cycling Soil formation and protection Water cycling Habitat provisioning Production of oxygen/ gas regulation

livestock grassland-based systems - - -

-livestock landless systems - - -

-Proportion of countries reporting

the Ps that report any effect of the

driver (%)

naturally regenerated forests - - -

-Planted forests - +/- +/- - +/- - +/- +/- +

self-recruiting capture fisheries +/- - - +/- - -

-Culture-based fisheries +/- - +/- +/- - +/- +/- - + ^10–17

Fed aquaculture +/- - - - +/- +/- +/- - +/- ^18–25

non-fed aquaculture 0 - +/- - +/- +/- +/- + +/- 26–33

irrigated crop systems (rice) - +/- - + +/- + - - - 34–42

irrigated crop systems (other) - - - +/- -

-rainfed crop systems - - -

-Mixed systems - +/- +/- +/- + + +/- +/-

+/-Notes: Countries were invited to report the effects (positive, negative or “no effect”) of this driver on the provision of each ecosystem service in each production system. If 50% or more of the responses for a given combination of production system and ecosystem service indicate the same trend (positive [+], negative [-] or “no effect” [0]) then this trend is indicated in the respective cell of the table. In other cases, mixed effects (+/-) are indicated. The colour scale indicates the proportion of countries reporting the presence of the respective system that report any effect of the driver (positive, negative or “no effect”) on the provision of the respective ecosystem service. See Section 1.5 for descriptions of the production systems and a discussion of ecosystem services. Analysis based on a total of 91 country reports.

Source: Country reports prepared for The State of the World’s Biodiversity for Food and Agriculture.

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