Climate change, combined with other stressors, is overwhelming the capacity of ecosystems to buffer the impacts from extreme events like fires, floods, and storms.

This finding is from chapter 8 of Climate Change Impacts in the United States: The Third National Climate Assessment.

Process for developing key messages: The key messages and supporting chapter text summarize extensive evidence documented in the Ecosystems Technical Input Report, Impacts of Climate Change on Biodiversity, Ecosystems, and Ecosystem Services: Technical Input to the 2013 National Climate Assessment.7406884d-2302-4644-aa50-12ed8baf4fd7 This foundational report evolved from a technical workshop held at the Gordon and Betty Moore Foundation in Palo Alto, CA, in January 2012 and attended by approximately 65 scientists. Technical inputs (127) on a wide range of topics related to ecosystems were also received and reviewed as part of the Federal Register Notice solicitation for public input.

Description of evidence base: The author team digested the contents of more than 125 technical input reports on a wide array of topics to arrive at this key message. The foundational Technical Input Report7406884d-2302-4644-aa50-12ed8baf4fd7 was the primary source used. Fires: Climate change has increased the potential for extremely large fires with novel social, economic, and environmental impacts. In 2011, more than 8 million acres burned, with significant human mortality and property damage ($1.9 billion).4d24a997-855e-44e0-9693-2895851d9144 Warming and decreased precipitation have made fire-prone ecosystems more vulnerable to “mega-fires” – large fires that are unprecedented in their social, economic, and environmental impacts. Large fires put people living in the urban-wildland interface at risk for health problems and property loss. Floods: Natural ecosystems such as salt marshes, reefs, mangrove forests, and barrier islands defend coastal ecosystems and infrastructure against flooding due to storm surges. The loss of these natural features due to coastal development, erosion, and sea level rise render coastal ecosystems and infrastructure more vulnerable to catastrophic damage during or after extreme events (see Ch. 25: Coasts).15451c8d-0add-40c7-a7e6-c286ccbf76f6 65b90ca8-fd21-4d15-9631-bae1dc6a63b6 Floodplain wetlands, which are also vulnerable to loss by inundation, absorb floodwaters and reduce the impact of high flows on river-margin lands. In the Northeast, a sea level rise of 1.6 feet (within the range of 1 to 4 feet projected for 2100; Ch. 2: Our Changing Climate, Key Message 9) will dramatically increase impacts of storm surge on people (47% increase) and property loss (73% increase) in Long Island.0fc3f3dd-7edf-4305-8ec9-0d0e2bcfcd18 Storms: Natural ecosystems have a capacity to buffer extreme weather events that produce sudden increases in water flow and materials. These events reduce the amount of time water is in contact with sites that support the plants and microbes that remove pollutants (Chapter 25: Coastal Zone).15451c8d-0add-40c7-a7e6-c286ccbf76f6 65b90ca8-fd21-4d15-9631-bae1dc6a63b6

New information and remaining uncertainties: A new analytical framework was recently developed to generate insights into the interactions among the initial state of ecosystems, the type and magnitude of disturbance, and effects of disturbance.41f4e895-d87d-427a-a9d9-e1d411fc838d Progress in understanding these relationships is critical for predicting how human activities and climate change, including extreme events like droughts, floods, and storms, will interact to affect ecosystems. Uncertainties: The ability of ecosystems to buffer extreme events is extremely difficult to assess and quantify, as it requires understanding of complex ecosystem responses to very rare events. However, it is clear that the loss of this buffering ecosystem service is having important effects on coastal and fire-prone ecosystems across the United States.

Assessment of confidence based on evidence: Given the evidence base and uncertainties, there is high confidence that climate change, combined with other stressors, is overwhelming the capacity of ecosystems to buffer the impacts from extreme events like droughts, floods, and storms. Ecosystem responses to climate change will vary regionally. For example, whether salt marshes and mangroves will be able to accrue sediment at rates sufficient to keep ahead of sea level rise and maintain their protective function will vary by region. Climate has been the dominant factor controlling burned area during the 20th century, even during periods of fire suppression by forest management,b95e9226-076c-4eb5-9367-472499624084 e1e1f3a0-9fea-4ad2-a3af-575716f9849e and the area burned annually has increased steadily over the last 20 years concurrent with warming and/or drying climate. Warming and decreased precipitation have also made fire-prone ecosystems more vulnerable to “mega-fires” – large fires that are unprecedented in their social, economic, and environmental impacts. Large fires put people living in the urban-wildland interface at risk for health problems and property loss. In 2011 alone, 8.3 million acres burned in wildfires, causing 15 deaths and property losses greater than $1.9 billion.4d24a997-855e-44e0-9693-2895851d9144

References :

• The rising tide: assessing the risks of climate change and human settlements in low elevation coastal zones (65b90ca8)
• Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity (e1e1f3a0)
• Continued warming could transform Greater Yellowstone fire regimes by mid-21st century (b95e9226)
• Cross-system comparisons elucidate disturbance complexities and generalities (41f4e895)
• Coastal impacts due to sea-level rise (15451c8d)
• Wildland Fire Summary and Statistics Annual Report 2011 (4d24a997)
• Assessing future risk: quantifying the effects of sea level rise on storm surge risk for the southern shores of Long Island, New York (0fc3f3dd)
• Impacts of Climate Change on Biodiversity, Ecosystems, and Ecosystem Services. Technical Input to the 2013 National Climate Assessment (7406884d)