The 128-page document continues theKnowledge for actionseries of books that provides professionals in the water and aquatic-environment sector (scientists, engineers, managers, instructors, students, etc.) with informa- tion on recent research and science-advice work.
The book is available on the Onema site:
(http://www.onema.fr/IMG/EV/cat7a-thematic-issues.html#action).
A hard copy of each document may be requested as long as stocks last.
Contact: veronique.barre@onema.fr
Translation:Bartsch&Cie-Graphicdesign:BéatriceSaurel-Printedby:IMEbyestimprim,2015
2
quatic environments constitute ecological treasure houses, represent a unique cultural heritage and provide society with important economic resources. In addition to direct human impacts, there is now increasing concern about the effects of climate change on aquatic environments.
What will be the consequences for water resources? How will fish react?
Is it possible to foresee the changes to come? Do we have the tools and means required to anticipate and mitigate the effects of climate change on fish populations?
This document briefly outlines the contents of the new book in theKnowledge for actionseries.
The reality of climate change is no longer an issue. According to the World meteorological organisation, 2013 tied with 2007 as the sixth hottest year ever recorded worldwide, thus confirming the observed long-term warming trend.
Temperatures were not unusual in continental France, however, a number of exceptional climatic events occurred such as the heavy snow and rainfall that led to flooding in the South-West of France and the storms Christian and Dirk.
In addition, the Intergovernmental panel on climate change (IPCC) recently increased to 0.6°C its estimate of the average surface temperature rise for the period 1951 to 2010.
This rapid change in climate conditions has led to thermal and hydrological modifications and severe upheaval in the functioning of aquatic environments may be expected.
ThisKnowledge for actionbook provides both general information on changes in hydrosystems and fish communities subjected to climatic forcing and the means to understand and use models within the limits of the uncertainty inherent to such tools.
Photo credits: N. Poulet - Onema (p1-2)
Florence Baptist, Nicolas Poulet
& Nirmala Séon-Massin
(coordinators)
Anticipating the impact of climate change on fish communities
Over the past few years, numerous tools have been developed to assess the impact of climate change on living organisms. Among those tools, statistical distribution models play an important role because they are based on simple assumptions and can project the potential habitat changes of a given species in response to different climate-change scenarios. The projections produced by the distribution models reveal trends that can be used to assess the vulnerability of each species and changes in the richness and composition of communities.
The statistical distribution models are precisely described to put readers in a position to identify the data required to use the models, the correct scale for data interpretation and the uncertainties inherent to the models. A number of scenarios on the future location of favourable habitats for freshwater fish in continental France produced by the models are also presented.
Taking action to reduce the vulnerability of fish communities
Adaptation to climate change is a complex phenomenon that is already well under way in continental France. The National plan for adaptation to climate change (PNACC) provided new impetus in 2011 by pulling together an array of separate initiatives and by coordinating a number of incentive and regulatory measures (Regional plan for climate, air and energy, Territorial climate-energy plan, etc.). In the water field, however, no new binding measures have been undertaken. That being said, the information presented in this chapter makes clear that the WFD measures already implemented constitute a highly effective tool in reducing the vulnerability of fish populations in a context of climate change.
The chapter makes clear that, in spite of the uncertainties surrounding climate and hydrological projections, climate change should be seen as a further argument to implement measures to mitigate pressures and thus enhance the resilience and adaptive capacity of environments and organisms.
Understanding the impact of climate change on water resources
The global climate has always fluctuated over time under the direct and indirect influence of various phenomena. However, human activities releasing greenhouse gasses (GHG) and aerosols have clearly caused changes in the climate since the end of the 1800s, resulting in increases in air temperatures and the average sea level, as well as a reduction in snow-covered surfaces and ice caps. Though a degree of uncertainty is inherent to their operation, the climate models unambiguously project a worsening of these phenomena with major consequences for the hydrological cycle.
This chapter reviews current and projected changes in the climate and hydrology, and also discusses the uncertainties inherent to the techniques implemented.
Chapter
The second chapter reviews the scientific literature on the impacts of climate change already observed on the physiology, seasonal activities and ranges of freshwater fish over the past few decades. The results discussed are based on experimental studies and the analysis of long series of monitoring data on fish populations. Three geographical areas are examined in detail, namely the Rhône and Seine basins and Lake Geneva.
Changes in fish communities in a context of climate change
The physiology, biological rhythms and distribution of fish depend on environmental factors such as temperature, hydromorphological conditions and water quality (dissolved oxygen, pollutant concentrations, etc.). Climate disruptions impact these factors and thus constitute a major source of change for fish species, in terms of their physiology, reproduction and growth functions, and seasonal rhythms. Even though the signs are still not very clear in some rivers and interpretation is difficult due to local anthropogenic pressures, the consequences of climate change are observable over France as a whole, notably concerning changes in the ranges of fish.
Change in annual average temperature at a depth of five metres in Lake Geneva (according to www.cipel.org).
Contribution of successive generations of Arctic charr to the population in Lake Geneva. Ovulation in Arctic charr is blocked if the water temperature at a depth of 100 metres exceeds 7°C (Gerdeaux, 2011).
Examples of favourable-habitat projections for a species (brown trout) that reacts negatively to climate change.
(a) Presence observed (n=2 703 out of 4 381 sampling stations, source Onema, 2000-2008, using electrofishing).
(b) Habitats projected as currently favourable.
(c) Habitats potentially favourable in the future according to the zero-dispersal scenario (scenario A1B for the period 2060 to 2089).
(d) Habitats potentially favourable in the future according to the unlimited-dispersal scenario (scenario A1B for the period 2060 to 2089).
The higher the number of models projecting a favourable habitat, the greater the probability that the river reach is in fact favourable for the species (Explore 2070 - MEDDE/Biotope, 2013).
0-25%
25-50%
50-75%
75-100%
©F.Melki.-Biotope ©Explore2070-MEDDE/Biotope,2013
By providing shade, riparian vegetation plays an important role in the temperature regime of rivers.
©N.Poulet-Onema
Chapter
Chapter
Chapter
4
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ContributionofsuccessivegenerationsofArctic charrtothepopulationinLakeGeneva(%)
Watertemperature(°C)
Annual average temperature at a depth of 100 metres (°C)
