Southeast

-- An overview prepared by Ezra Millstein (World Wildlife Fund) -- 
 

Climate and changes in it – regardless of their cause – matter to people, communities and businesses. Global warming is likely to bring many changes to the nation. The United States as a whole is in a strong economic position to adapt to many of these changes, but adaptation is often expensive, not always possible or successful, and during transitions ecosystems, communities, and individuals could suffer. Moreover, national impact summaries disguise local dislocations and disruptions to the ways we live, work and recreate. Climate change adds a serious stress to our already threatened resources and treasured places. Overall impact statements also mask significant opportunities. To minimize the negative changes and make the most of the positive changes we need to take a close look at how climate change will affect each region. How will the Southeast experience the effects of global warming? And how can we respond?

Climate Projections for the Southeast

Current climate models project regional temperature increases between 4 and 10°F by 2100, with an 8 to 15°F increase in the average summer heat index. Models differ on the changes in precipitation in the Southeast.  One of the models used in the National Assessment (the Canadian model) projects less precipitation on average than at present while another model (the Hadley model) simulates more precipitation than at present. This difference has serious hydrological implications for the region.  Models also project an increase in heavy downpour events nationally whether or not average precipitation increases.

Changes consistent with some of the model projections have already occurred in the Southeast.  For example, over the past 50 years the average annual length of the snow season has decreased by 4 days regionally.  Precipitation trends show increases of 20-30% or more during the past century across Mississippi, Louisiana, Arkansas, South Carolina and Alabama, and more moderate increases in the rest of the region. Much of the precipitation has been associated with more intense events, which is more likely to cause flooding throughout the region. 

Key Findings
 

Global warming adds a significant stress to regions already experiencing intense development and population pressures. The National Assessment highlights five key issues for the region, which are dealt with in more detail in the forthcoming Southeast Regional Assessment: weather-related stresses on human population; agricultural crop yields, forest productivity shifts; water quality stresses; and threats to coastal areas.

Weather related stresses on human populations
The US experienced 42 weather-related disasters over the past 20 years that resulted in damage/costs in excess of $1 billion each; 23 of these occurred in the Southeast, mostly in the form of floods and hurricanes. Projected sea-level rise could increase the risk from flooding to low-lying coastal counties from the Carolinas to Texas, which could adversely impact human health, threaten lives and cause extensive economic damage. Heat waves also take their toll; the southern drought of 1998 resulted in damages in excess of $6 billion. The same year, a combination of an unusually wet winter, dry summer and high heat led to wildfires in Florida that burned roughly 500,000 acres of land.  Heat waves increase the risks of heat related illness and mortality and increase ozone production affecting primarily the elderly, the young and those who are already suffering from respiratory or other illnesses.

Agricultural crop yields
Crop models employed in the assessment used two climate scenarios to estimate the effects of climate change on five Southeastern crops: corn, soybeans, peanuts, winter wheat and rice. The wetter scenario (using the Hadley Centre climate model) suggested that crop yields could be enhanced with the increased rainfall and higher CO2 concentrations (which fertilize crops) that accompany higher temperatures. In addition, irrigation needs could be reduced if temperatures rise no more than 3-4°F. However, the drier scenario (using the Canadian climate model) resulted in major reductions in all crop yields at most locations. The largest threat to Southeastern crop yields appears to be decreases in precipitation accompanied by increases in temperature as projected by the Canadian model. Higher temperatures may also tax water resources leading to an increase in competition among water users and overall declines in water availability. 

Forest productivity shifts
Using the wetter scenario (the Hadley climate model), forest productivity models indicate a 14% increase in overall forest productivity by 2100, with hardwoods becoming much more productive than softwoods, like pines (which currently account for 2/3 of the region’s forest production). Both models used in the assessment predict a northward shift in forest productivity over the next century. As a result, timber markets would shift to the mid-Atlantic region which is likely to experience more favorable growth conditions than the South, though prices and inventories are difficult to predict given the many market forces influencing timber values and preferences. 

Water quality stresses
Changes in climate can cause decreased runoff during early summer, reducing water quality in the Southeast.  Low water flows also reduce dissolved oxygen content, which can result in massive fish kills and harmful algal blooms in coastal and inland waters. Existing human stresses on water quality are already frequent and could be exacerbated during extreme conditions such as the droughts that are predicted to increase according to one climate scenario used in the assessment. Depending on the climate scenario used, projections include up to a 10% decline in summer streamflow during Southeast summer months over the next 30 years. On the other hand, if rainfall in the Upper Mississippi Valley increases, as some climate models project, river discharge and nutrient flux throughout the Southeast could be affected.  This would result in higher nitrogen and phosphorus concentrations in rivers, and an increased risk of hypoxia (oxygen depletion) in the Gulf of Mexico with negative impacts on commercial and recreational fisheries.

Threats to coastal areas
Assuming the rate and magnitude of global warming projected in climate models, the rate of sea-level rise could increase as much as 2 to 5-fold over the next century, threatening low-lying marshes, barrier islands, and coastal communities. Coastal forests will be affected, along with estuaries and aquatic plant communities.  Where possible, coastal ecosystems could migrate inland; however, in many cases human development poses an obstacle to that migration. The impact from storm surge will intensify as sea level rises and natural coastal defenses deteriorate. Thus, even if hurricanes do not become more frequent and intense, they are likely to cause more damage.  In 1995, Florida topped the list of coastal states with potential hurricane damages, with $872 billion in insured properties. 

Adapting to the Potential Impacts of Global Warming
 

The Southeast may bear a significant burden from the impacts of climate change. Climate scientists agree that further climate change may be inevitable and will therefore require adaptation, although most scientists also think that the pace of climate change can be slowed by substantially reducing greenhouse gas emissions. This would give governments, businesses, and ecosystems around the world more time to respond and adapt to climate change as well as reducing the overall severity of climate change-related impacts, thereby buying "insurance" for an uncertain future.  Another way to buy insurance now is to incorporate climate change into all long-term decisions about natural resources, thereby providing greater resilience.

Future adaptation strategies for addressing weather-related stresses on human populations could include development of health advisory systems, community-wide heat emergency plans, improved weather prediction capabilities, and other actions that are presented in the Southeast and Health chapters of the National Assessment. Technological advances and adaptive management practices could minimize adverse effects on crop yields, while a shift to crops that are optimal for the new climate can be implemented. Planting dates, harvest schedules and species and varieties cultivated can be adjusted. Adaptations for protecting forest productivity may include bioengineering, reduction of air pollutants, use of marginal agricultural land for tree production, intensive forest management and silvicultural system improvements.  Areas of high property value could be protected against sea-level rise by seawalls or other hard structures though these adaptation measures are costly, not always effective in the long term, and likely to result in beach loss in front of the structure. Protecting natural coastal communities and ecosystems from the impacts of climate change will be very challenging. However, management measures such as increasing protection of coastal wetlands, limiting certain coastal construction, sediment diversions for dams, developing plant and animal migration corridors, invasive species control, coastal restoration, water control structures for wetlands, and removal of other stresses may increase the resiliency of these areas.

Where do we go from here?

There remain uncertainties in predicting future impacts. Climate models must be improved, and approaches for modeling human health impacts should include more detail. It is important to examine the effects of climate variations on animal management practices, pests and pest management systems, and high value crops such as citrus and vegetables. New genetic agricultural varieties must be explored, and pilot studies should examine biotechnology transfer. We must develop a greater understanding of the synergistic impacts of environmental change on southern forests, and improve development, testing and validation of integrated stress impacts through computer modeling. Pollutant loadings and biophysical reactions must be studied in order to accurately predict the impacts of climate change on southeastern water resources. It will be beneficial to develop a greater understanding of the role of disturbance in natural ecosystems, and improve our ability to predict climate extremes, so that we can better adapt to climate change impacts.

Additional Information
Confronting Climate Change in the Gulf Coast Region, a comprehensive report by the Union of Concerned Scientists and the Ecological Society of America on the potential impacts of climate change along the gulf coast of the US.

For additional information you can contact:

Ezra Millstein, World Wildlife Fund
 Tel.: (954) 921-7599  Email: ezra.millstein@wwfus.org