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Drought

Stressors

Drought

Drought trends in the Northeast
The Northeast is generally considered to be a moist region with ample rain and snow, but droughts are not uncommon. Widespread drought has occurred across the region as recently as 2016, and before that in the early 2000s, 1980s, and mid-1960s. More frequent and severe droughts are expected as climate change continues to increase temperatures, raise evaporation rates, and dry out soils - even in spite of more precipitation and heavier rainfall events.

Annual projections indicate an overall increase in precipitation (top graph), with continued summer dry spells (bottom graph). Note: Observational records go through  2005 and the model begins projecting in 2006. The 2016 drought is not reflected in these graphs. This figure is based on a single model and is only one of many possible futures. It does not provide a prediction of timing of future dry periods, only an indication of the expected variability of summer rainfall in relation to past variability.
Annual projections indicate an overall increase in precipitation (top graph), with continued summer dry spells (bottom graph). Note: Observational records go through 2005 and the model begins projecting in 2006. The 2016 drought is not reflected in these graphs. This figure is based on a single model and is only one of many possible futures. It does not provide a prediction of timing of future dry periods, only an indication of the expected variability of summer rainfall in relation to past variability. Figure courtesy of Ambarish Karmalkar, NE CSC.

Increasing Variability in Precipitation
Extreme precipitation events have been increasing across the Northeast.6

  • Between 1958 and 2012, the amount of precipitation that fell in very heavy events (heaviest 1% of all daily events) increased by over 70% in the Northeast, more than in any other part of the country.12
  • When Massachusetts is already in a relatively dry period, warmer temperatures will have a larger impact on drought.
  • Warmer temperatures will likely mean less snow in the winter, resulting in decreased snowmelt in spring when most plants need it most.
  • The annual maximum number of consecutive dry days (days with less than 0.04 inches of precipitation) is expected to increase by 1-10 days regionally for the period 2070-2099 compared to 1971-2000,12 though observations suggest consecutive dry days have been declining in our region.10

Annual precipitation across the Northeast varies, with the highest amounts occurring in the mountains and coastal areas. Increased variability and unpredictability in precipitation will likely cause negative ecological impacts on species and ecosystems, such as changes to biodiversity, species distributions, and productivity, if they are not able to adapt to change.

Changes in Future Droughts
Long-term research and monitoring of terrestrial and aquatic ecosystems, from headwater streams to coastal wetlands and fisheries, provides a long record of drought within the region. These records indicate that, historically (1960s, 1980s, and early 2000s), droughts have been more frequent and severe in the Northeast than those encountered in the distant past (based on paleoclimate records spanning back thousands of years). Even though annual precipitation is projected to increase throughout this century, summers could experience more variable and severe dry spells based on increasing temperatures and less frequent precipitation (though we note that projections of future precipitation changes are less certain than for temperatures).5

Conceptual diagram illustrating shifts in Northeast and Midwest seasonal patterns due to climate change. Diagram courtesy of the Integration and Application Network, University of Maryland Center for Environmental Science.
Conceptual diagram illustrating shifts in Northeast and Midwest seasonal patterns due to climate change. Diagram courtesy of the Integration and Application Network, University of Maryland Center for Environmental Science.

Changes in Seasonal Water Regimes
Seasonal or short-term droughts that last less than 6 months are most common in the Northeast and are expected to occur more frequently.5,9 The greatest risk for seasonal drought may be in summer and early fall as a result of higher temperatures that lead to greater evaporation and earlier snowmelt.3,5,6 Earlier winter and spring snowmelt further reduces the length of time that snow stays on the ground.6,11,12 Low water levels in spring and summer could cause earlier droughts that last longer into the growing season. Longer, drier summers may prolong drought conditions and worsen the drought’s effects on the region’s ecosystems. Heat waves are expected to become more frequent, intense, and longer in duration across the Northeast as well.11 Extremely hot days combined with a reduction in soil moisture will exacerbate drought conditions and increase plant heat stress, especially in spring, summer, and fall.11

Historical (black line) and projected seasonal averages of soil water storage (amount of water stored in the soil column) in Massachusetts according to an average of 33 downscaled CMIP5 models. A low (RCP 4.5) scenario of projected changes is shown in blue and a high scenario (RCP 8.5) in red. Solid lines show average model results and their standard deviations are indicated by the respective shaded envelopes. Data and graphs are courtesy of the USGS National Climate Change Viewer.
Historical (black line) and projected seasonal averages of soil water storage (amount of water stored in the soil column) in Massachusetts according to an average of 33 downscaled CMIP5 models. A low (RCP 4.5) scenario of projected changes is shown in blue and a high scenario (RCP 8.5) in red. Solid lines show average model results and their standard deviations are indicated by the respective shaded envelopes. Data and graphs are courtesy of the USGS National Climate Change Viewer.

 

 

 

 

 

Impacts on Massachusetts wildlife and habitats
“Ecological drought” describes impacts on ecological systems, including:

  • Decreased plant growth and productivity
  • Increased wildfires
  • Greater insect outbreaks
  • Increased local species extinctions
  • Reduced water availability and habitat for aquatic species
  • Lower stream flows and freshwater delivery to downstream estuarine habitats
  • Potential increases of saltwater intrusion into coastal ecosystems
  • Changes in the timing, magnitude, and strength of mixing (stratification) in coastal waters
  • Increased potential for hypoxia (low oxygen) events
  • Reduced forest productivity
  • Direct and indirect effects on goods and services provided by habitats (such as timber, carbon sequestration, recreation, and water quality from forests)2

The biggest drought risk to our ecosystems may occur when decreases in water availability interact with other emerging climate-driven stressors, including:

Our existing regional forests grew during a time period when there was relatively ample water available. As a result, many species in Massachusetts are drought-intolerant, such as bats, salamanders, toads, freshwater fishes, and mussels. Consequently, these species and their supporting habitats depend on current seasonal water regimes and are highly vulnerable to changes in where, how, and when water is delivered.

Our understanding of the effects of drought on ecosystems is greatly improving, but modeling species’ interactions in response to drought is complex and remains an active area of research. For instance, whether forest populations will be able to migrate to regions that have more suitable climates in the future remains unsure.2

Broad-scale drought conditions across Massachusetts as of the start of the water year (September 27, 2016). Note that this map shows broad-scale drought conditions, and local conditions may vary. This map shows that the recent drought of 2016 has affected much of the state. Photo credit: U.S. Drought Monitor
Broad-scale drought conditions across Massachusetts as of the start of the water year (September 27, 2016). Note that this map shows broad-scale drought conditions, and local conditions may vary. This map shows that the recent drought of 2016 has affected much of the state. Photo credit: U.S. Drought Monitor

Management strategies
The Northeast is home to nearly half of the U.S. population. It contains a large network of supporting infrastructure as well as diverse ecosystems.6 Human water use, such as for water supply, irrigation, and hydropower production, competes with environmental flows for aquatic species and other ecological services during periods of drought. This complicates water management actions and coordination in Massachusetts and is further complicated by diverse private and public land ownership.

Changes in how humans respond to drought (e.g., increased irrigation) can increase competition for ecologically available water and pose substantial threats to ecosystems, even if supply (precipitation) increases. Proactive strategies that consider the interaction of drought impacts with other stressors (urbanization, sea level rise, invasive species, etc.) are becoming increasingly important.

References

1. Catanzaro, P., A. D’Amato, and E.S. Huff. 2016. Increasing Forest Resiliency for an Uncertain Future. U.S. Department of Agriculture, Northeast Climate Science Center, and Northern Institute of Applied Climate Science, 32 p.

2. Clark, J.S., L. Iverson, C.W. Woodall, C.D. Allen, D.M. Bell, D.C. Bragg, A.W. D’Amato, F.W. Davis, M.H. Hersh, I. Ibanez, et al. 2016. The impacts of increasing drought on forest dynamics, structure, and biodiversity in the United States. Global Change Biology, 22, 2329–2352. doi: 10.1111/gcb.13160.

3. Frumhoff, P.C., J.J. McCarthy, J.M. Melillo, S.C. Moser, and D.J. Wuebbles. 2007. Confronting Climate Change in the U.S. Northeast: Science, Impacts, and Solutions. Synthesis report of the Northeast Climate Impacts Assessment (NECIA). Cambridge, MA: Union of Concerned Scientists (UCS).

4. Groisman, P. Y., R. W. Knight, and O. G. Zolina. 2013: Recent trends in regional and global intense precipitation patterns. Climate Vulnerability, R. A. Pielke, Sr., Ed., Academic Press, 25-55.

5. Hayhoe, K., C.P. Wake, T.G. Huntington, L. Luo, M.D. Schwartz, J. Sheffield, E. Wood, B. Anderson, J. Bradbury, A. DeGaetano, T.J. Troy, and D. Wolfe. 2006: Past and future changes in climate and hydrological indicators in the U.S. Northeast. Climate Dynamics, DOI: 10.1007/s00382-006-0187-8.

6. Horton, R., G. Yohe, W. Easterling, R. Kates, M. Ruth, E. Sussman, A. Whelchel, D. Wolfe, and F. Lipschultz. 2014. Ch. 16: Northeast. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 16-1-nn.

7. Karl, T. R., J. T. Melillo, and T. C. Peterson, Eds., 2009. Global Climate Change Impacts in the United States. Cambridge University Press, 189 pp. Online at http://downloads.globalchange.gov/usimpacts/pdfs/climate-impacts-report.pdf.

8. Massachusetts (MA) Drought Management Plan. 2013. Massachusetts Executive Office of Energy and Environmental Affairs and Massachusetts Emergency Management Agency. 41 p. Online at: http://www.mass.gov/eea/docs/eea/wrc/droughtplan.pdf.

9. National Oceanic and Atmospheric Administration (NOAA). 2016. Drought Impacts and Outlook: Northeast Region, July 2016. Northeast Regional Climate Center. Online at: www.drought.gov/drought/resources/reports.

10. Thibeault, J.M. and A. Seth. 2014. Changing climate extremes in the Northeast United States: observations and projections from CMIP5. Climatic Change, 127: 273. doi:10.1007/s10584-014-1257-2.

11. U.S. Environmental Protection Agency (EPA): Climate Impacts in the Northeast. Online at: https://www.epa.gov/climate-impacts/climate-impacts-northeast#main-content.

12. Walsh, J., D. Wuebbles, K. Hayhoe, J. Kossin, K. Kunkel, G. Stephens, P. Thorne, R. Vose, M. Wehner, J. Willis, D. Anderson, S. Doney, R. Feely, P. Hennon, V. Kharin, T. Knutson, F. Landerer, T. Lenton, J. Kennedy, and R. Somerville. 2014. Ch. 2: Our Changing Climate. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 19-67. doi:10.7930/J0KW5CXT.

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