Observed monitoring data and predictive modelling help understand ongoing and future vulnerability of Chesapeake Bay watershed stream fish communities to climate and land-use change
Issue: The Chesapeake Bay Watershed (CBW) is experiencing effects of climate (warming temperatures and shifting precipitation patterns) and land-use/land-cover (LULC; transition from forest or agriculture to developed lands) change, and these trends are likely to continue under future scenarios of warming and population growth. Stream biodiversity may be vulnerable to ongoing and future climate and LULC change in the CBW, potentially jeopardizing the economic and recreational benefits that CBW residents receive from stream ecosystems.
To help protect and restore CBW stream biodiversity, the Chesapeake Watershed Agreement aims to maintain the status of healthy watersheds, monitor and assess trends in climatic conditions (particularly stream temperature) and their effects on CBW ecosystems, and better understand the impacts of LULC on CBW biodiversity.
USGS Study
The USGS examined the vulnerability of stream fish biodiversity to climate and LULC change throughout the CBW in contemporary (1996 – 2016) and projected future (2030, 2060, 2090) periods. Stream fish biodiversity responses were examined using species characteristics that describe why and how species may be vulnerable or resilient to climate and LULC change. To understand contemporary trends, researchers analyzed observed time-series data on fish communities and environmental conditions at 21 well-sampled streams. To assess future impacts, researchers used climate and LULC scenarios that characterized a variety of temperature, precipitation, and land-use changes to project changes in fish community characteristics at all CBW streams. Researchers also compared observed trends in environmental conditions and stream biodiversity to future model projected changes to better understand the potential reality of modelled scenarios.
Major Findings
Observed trends in climate, LULC, and stream fish biodiversity at well-sampled CBW streams:
- Observed climate trends (1996-2016) revealed streams became warmer and drier during summer periods. Observed LULC change indicated shifts from agricultural land toward developed land-use in Piedmont streams.
- Stream fish communities responded to observed climate and LULC revealed by increasing dominance of carnivorous species that preferred warmer-water and finer, silty substrates.
- Observed changes in fish communities were greater in Piedmont streams exposed to both LULC and climate change relative to streams in Shenandoah National Park which only experienced climatic change.
Model projected future trends in climate, LULC, and fish biodiversity at all CBW streams:
- Future (2030-2090) climate scenarios indicated that CBW environments may become warmer and drier during summer. LULC scenarios forecasted increasing proportions of developed land-use, particularly in Coastal Plains and Piedmont streams.
- Models projected future losses in suitable habitat for fishes that prefer cold-water, clean substrates, and fast-flowing waters. These losses in habitat suitability were likely to be particularly severe in upland (Appalachian) regions and smaller habitats (headwaters – small rivers) within these regions.
- On the other hand, models projected gains in habitat suitability for carnivorous fishes that preferred warmer-water, finer substrates, and slower waters and these gains were most prevalent in Piedmont streams.
Comparison of observed and future trends:
- Comparing observed time-series trends to future projections indicated ongoing shifts in fish communities may be consistent with modelled projections, particularly in Piedmont regions undergoing urbanization.
Management Applications
The combined observed and projected future trend analyses can help managers better understand environmental changes in the CBW and how stream fish communities may respond to these conditions. Some examples where results can be applied to Chesapeake Watershed Agreement management strategies are:
- Using modelling results to assess trends in climate conditions throughout the CBW and understanding the vulnerability of CBW ecosystems to climate change.
- Monitoring land-use conversion from agriculture and forest and levels of imperious surface throughout the CBW and understanding the impacts of LULC change on streams, watersheds and communities.
- Helping state efforts to identify, protect, and track healthy watersheds.
For More Information
The study has been published in Global Change Biology: Woods, T., Freeman, M.C., Krause, K.P. and Maloney, K.O., 2023. Observed and projected functional reorganization of riverine fish assemblages from global change. Global Change Biology. https://doi.org/10.1111/gcb.16707. The project team included Taylor Woods, Mary Freeman, Kevin Krause, and Kelly Maloney. For further information or to request a briefing on this research, please contact Taylor Woods at (tewoods@usgs.gov).
Issue: The Chesapeake Bay Watershed (CBW) is experiencing effects of climate (warming temperatures and shifting precipitation patterns) and land-use/land-cover (LULC; transition from forest or agriculture to developed lands) change, and these trends are likely to continue under future scenarios of warming and population growth. Stream biodiversity may be vulnerable to ongoing and future climate and LULC change in the CBW, potentially jeopardizing the economic and recreational benefits that CBW residents receive from stream ecosystems.
To help protect and restore CBW stream biodiversity, the Chesapeake Watershed Agreement aims to maintain the status of healthy watersheds, monitor and assess trends in climatic conditions (particularly stream temperature) and their effects on CBW ecosystems, and better understand the impacts of LULC on CBW biodiversity.
USGS Study
The USGS examined the vulnerability of stream fish biodiversity to climate and LULC change throughout the CBW in contemporary (1996 – 2016) and projected future (2030, 2060, 2090) periods. Stream fish biodiversity responses were examined using species characteristics that describe why and how species may be vulnerable or resilient to climate and LULC change. To understand contemporary trends, researchers analyzed observed time-series data on fish communities and environmental conditions at 21 well-sampled streams. To assess future impacts, researchers used climate and LULC scenarios that characterized a variety of temperature, precipitation, and land-use changes to project changes in fish community characteristics at all CBW streams. Researchers also compared observed trends in environmental conditions and stream biodiversity to future model projected changes to better understand the potential reality of modelled scenarios.
Major Findings
Observed trends in climate, LULC, and stream fish biodiversity at well-sampled CBW streams:
- Observed climate trends (1996-2016) revealed streams became warmer and drier during summer periods. Observed LULC change indicated shifts from agricultural land toward developed land-use in Piedmont streams.
- Stream fish communities responded to observed climate and LULC revealed by increasing dominance of carnivorous species that preferred warmer-water and finer, silty substrates.
- Observed changes in fish communities were greater in Piedmont streams exposed to both LULC and climate change relative to streams in Shenandoah National Park which only experienced climatic change.
Model projected future trends in climate, LULC, and fish biodiversity at all CBW streams:
- Future (2030-2090) climate scenarios indicated that CBW environments may become warmer and drier during summer. LULC scenarios forecasted increasing proportions of developed land-use, particularly in Coastal Plains and Piedmont streams.
- Models projected future losses in suitable habitat for fishes that prefer cold-water, clean substrates, and fast-flowing waters. These losses in habitat suitability were likely to be particularly severe in upland (Appalachian) regions and smaller habitats (headwaters – small rivers) within these regions.
- On the other hand, models projected gains in habitat suitability for carnivorous fishes that preferred warmer-water, finer substrates, and slower waters and these gains were most prevalent in Piedmont streams.
Comparison of observed and future trends:
- Comparing observed time-series trends to future projections indicated ongoing shifts in fish communities may be consistent with modelled projections, particularly in Piedmont regions undergoing urbanization.
Management Applications
The combined observed and projected future trend analyses can help managers better understand environmental changes in the CBW and how stream fish communities may respond to these conditions. Some examples where results can be applied to Chesapeake Watershed Agreement management strategies are:
- Using modelling results to assess trends in climate conditions throughout the CBW and understanding the vulnerability of CBW ecosystems to climate change.
- Monitoring land-use conversion from agriculture and forest and levels of imperious surface throughout the CBW and understanding the impacts of LULC change on streams, watersheds and communities.
- Helping state efforts to identify, protect, and track healthy watersheds.
For More Information
The study has been published in Global Change Biology: Woods, T., Freeman, M.C., Krause, K.P. and Maloney, K.O., 2023. Observed and projected functional reorganization of riverine fish assemblages from global change. Global Change Biology. https://doi.org/10.1111/gcb.16707. The project team included Taylor Woods, Mary Freeman, Kevin Krause, and Kelly Maloney. For further information or to request a briefing on this research, please contact Taylor Woods at (tewoods@usgs.gov).