Climate Change Impacts On Lakes
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Human activities that burn fossil fuels emit gases (primarily CO2 and CH4) that accumulate in the atmosphere and trap heat. There remains little credible debate that our climate is changing and it is expected that these changes will likely result in extreme climate fluctuations (e.g., changes in frequency and intensity of storms and floods), increases in global water temperatures, reductions in ice cover, and biotic changes. Climate change will affect our land and water resources, and our economy; these profound impacts have obvious resource management and policy implications. Globally, researchers have been investigating the impacts of future climate change on lake and freshwater ecosystems for over two decades, and several comprehensive reports have been published by the Intergovernmental Panel on Climate Change (IPCC). This position statement discusses three topics: projected future climate, likely changes to lakes and freshwater systems, and suggested actions for lake and water resource managers.
Projected Future Climate
Relative to the period from 1850-1900, global surface temperature is likely to rise by 1.5-2°C by the end of the 21st century (IPCC, 2013). More specifically for the next twenty years (2016-2035), a global temperature increase is predicted in the range of 0.3-0.7°C compared to 1986-2005. With virtual certainty, the IPCC states that there will be more frequent hot and less frequent cold temperature extremes over land. While changes in precipitation are difficult to predict, modeling suggests that the contrast between precipitation in wet and dry regions, as well as wet and dry seasons, will increase. In general, more extreme precipitation events will become more common and more intense in mid-latitude and wet tropical regions (IPCC, 2013). Specifically in North America, winter warming will be greatest in Alaska, Canada and Greenland, while summer maximum warming will occur in Western, Central and Eastern North America (Christensen, 2013).
Climate Change Impacts on Freshwater Systems
Aquatic ecosystems are sensitive to climate change, and the impacts of future climatic changes include a wide range of negative consequences (EPA, 2014). There may be increased flooding, pollutant transport, sediment erosion, and extended droughts from more frequent extreme events. Increased water temperatures will affect oxygen regimes, redox potentials, lake stratification, mixing rates, and the metabolism and life cycles of aquatic organisms (Kundzewicz, 2007). Freshwater species are at especially high risk to be threatened or endangered due to climate change (Millennium Ecosystem Assessment, 2005). However, specific ecological responses to climate change cannot be predicted, because new combinations of native and non-native species will interact in novel situations. Overall, shifts in precipitation variability and seasonal runoff will have profound effects on water supply, water quality, and management of water resources.
Possible Impacts to Lakes and Wetland Systems*:
- Declining lake and wetland levels may increase re-suspension of bottom sediments, release sediment-bound nutrients and toxins, and cause decreases in dissolved oxygen, especially during periods of ice cover.
- Declines in the duration of winter ice can have both positive and negative impacts on lakes and their ecosystems.
- On the positive side, shorter winter ice cover may reduce the likelihood for winter fish kills in shallow lakes;
- On the negative side, a shorter ice-free period will increase the growing season for rooted plants (including non-native species) to grow, which can lead to a variety of problems that may further inhibit aquatic recreation. Algal growth may also increase. An overabundance of algae has the potential to shift lakes to a turbid state, reducing aquatic plant growth and the related habitat benefits. An extended open water season may increase the occurrence and significance of internal P recycling. In regions of North America where tourism is dependent on ice cover, there will be declines in those forms of recreation and the dollars generated. On lakes with large surface areas such as the Great Lakes, increases in evaporation can be significant and result in lower water levels.
- Alteration in the distribution of many fish species: cold and cool-water species will decline in regions on the southerly edge of their range (e.g. lake trout in northern Minnesota, which represent the southern edge of their natural range) and warm-water species will expand northward.
- Successful invasions of nonnative species will be more likely as those organisms may prosper in regions where cold temperatures may have previously been a limiting factor.
- The duration of summer stratification will increase, adding to the risk of oxygen depletion over greater areas and for longer periods of time. Hypolimnetic temperatures would also be expected to increase in regions without ice cover.
- Fish, algal, and zooplankton growth rates should increase, but not at the same rate for each species. Rates of metabolism will also increase across trophic levels.
- Warmer lake waters; native plant and animal species responses will differ to changes in water temperature and hydrology.
- Increased incidence of harmful algal blooms due to declining lake levels and increasing water temperature (Paerl and Hulsman 2009).
- Increased sediment and nutrient loading due to larger rainfall events which can have profound impacts on lakes and in particular reservoirs, where sediment infilling can be a major problem (shorten design life).
- Extreme storm events will need to be factored into stormwater and wastewater treatment design, and in the implementation of watershed best management practices and flood control.
- Increased risk of pollutants, such as pesticides, water borne diseases, organic matter, and heavy metals entering water bodies during large events.
- Changes in the annual pattern of streamflow will alter many ecosystem processes with potential direct societal costs.
- Reduction in ecosystem services from aquatic ecosystems.
- Increased vulnerability of coastal wetlands to sea-level rise.
- Alteration in residence times of lake and wetland systems.
- Low water levels and/or drought conditions will lead to increased competition between consumptive uses and natural ecosystem needs for water resources.*This list provides examples of possible impacts and is by no means comprehensive.
Actions for Citizens and Policymakers
NALMS supports the following three ‘prudent and responsible’ actions for citizens and policymakers, as provided by Kling et al. (2003):
- Anticipate and plan for the regional impacts of climate change to reduce future damage.
- Reduce contributions to the global problem of heat-trapping greenhouse gas emissions
- Minimize human pressures on the global and local environment to reduce the vulnerability of ecosystems. Prudent actions include: reducing air pollution, protecting the quality of water supplies and aquatic habitat, reducing urban sprawl, reducing habitat destruction and fragmentation, restoring critical habitats, and preventing the spread of invasive nonnative species.
These actions should be addressed immediately. In addition to preventing or minimizing environmental and societal impacts, these actions will also result in benefits that include cost savings, cleaner air and water, improved habitat and recreation, and enhanced quality of life.
In addition, the IPCC authors propose that current water management practices are likely to be inadequate to reduce the negative impacts of climate change on water supply reliability, flood risk, and aquatic ecosystems. Ecosystem managers will need to assess current practices to determine which ones remain viable and where they will need to adaptively implement new practices.
Considerations for Lake and Aquatic Systems Managers:
- Identify the predicted local changes to lakes and their ecosystems and use this information to discuss climate change and resiliency with community members.
- Implement sampling and analysis schemes that will enable lake managers to identify changes early and to guide responses.
- Reduce nutrient loading to lakes by protecting healthy wetlands and restoring degraded wetlands to enhance nutrient uptake and reduce nutrient loading.
- Work with local municipalities to incorporate wetland protection and enhancement into their climate-ready responses.
- Minimize groundwater pumping for irrigation, or human/animal consumption that removes water from aquatic and wetland ecosystems.
- Consider using climate scenarios to assess possible future hydrologic changes, especially when considering water management projects with a long lifespan (both how the project may be affected by climate change and how the project may have either negative or positive impacts on the ecosystem as climate does change).
- Increase preparedness for extreme events and assess resilience of local ecosystem to climatic shifts.
- Consider natural and ecological solutions and develop lake management strategies that value the natural ecosystem services rather than gray infrastructure or quick solutions, which may increase vulnerability to extreme weather.
- Consider shifts in fisheries management and farming activities that will increase resilience to climate shifts and encourage water conservation.
Our job as lake managers has become more challenging. All of the lake and watershed protection and management activities that NALMS advocates will become more critical and important as a result of the impacts of climate change.
- NALMS should develop capacity for climate change adaptation by increasing collaboration and resource sharing with other water resource management organizations and agencies.
- NALMS should continue to include climate change as a topic at annual symposium and should pursue other avenues for increasing communication and outreach for issues of climate change and lake management.
- NALMS should be active in developing guidance for lake managers or communities to access weather data, information and/or tools in order to build capacity for local planning for climate-related changes to lake and aquatic systems.
Christensen, J.H., K. Krishna Kumar, E. Aldrian, S.-I. An, I.F.A. Cavalcanti, M. de Castro, W. Dong, P. Goswami, A. Hall, J.K. Kanyanga, A. Kitoh, J. Kossin, N.-C. Lau, J. Renwick, D.B. Stephenson, S.-P. Xie and T. Zhou, 2013: Climate Phenomena and their Relevance for Future Regional Climate Change. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
IPCC, 2013: Summary for Policymakers. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
EPA, 2014: Climate Impacts on Water Resources. http://www.epa.gov/climatechange/impacts-adaptation/water.html. Accessed on 1/28/15.
Kling, G., K. Hayhoe, L.B. Johnson, J.J. Magnuson, S. Polasky, S.K. Robinson, B.J. Shuter, M.M. Wander, D.J. Wuebbles and D.R. Zak, 2003: Confronting Climate Change in the Great Lakes Region: Impacts on Our Communities and Ecosystems. Union of Concerned Scientists / The Ecological Society of America. Cambridge, MA. [Available online: ucsusa.org/greatlakes]
Kundzewicz, Z.W., L.J. Mata, N.W. Arnell, P. Döll, P. Kabat, B. Jiménez, K.A. Miller, T. Oki, Z. Sen and I.A. Shiklomanov, 2007: Freshwater resources and their management. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson Eds., Cambridge University Press, Cambridge, UK, 173-210.
Millenium Ecosystem Assessment, 2005: Our human planet: summary for decision-makers. Island press.
Paerl H W and J Hulsman, 2009: Climate change: a catalyst for global expansion of harmful cyanobacterial blooms. Environ. Micro. Reports. 1(1), 27-37
Initially adopted by the NALMS Board of Directors on February 26, 2004. Amendments adopted by the NALMS Board of Directors on February 5, 2015.