Ecosystems help maintain a stable climate

• This eco-wheel image shows the natural resources that help stabilize climate, the benefits, and drivers of change. The earth's climate is constantly changing on geologic time scales ranging from centuries to thousands of millennia (e.g., periods of wide-spread volcanism, cooling or ice ages, etc.).
• Most species, including humans, have evolved or adapted to survive and flourish under such slowly changing patterns of temperature and precipitation averages, variability, and extremes. 
• Recently, these patterns have been changing more rapidly in response to increased levels of carbon dioxide (CO₂) and other greenhouse gasesgreenhouse gasesGases in the Earth's atmosphere that produce the greenhouse effect. Changes in the concentration of certain greenhouse gases, due to human activity such as fossil fuel burning, increase the risk of global climate change. Greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, halogenated fluorocarbons, ozone, perfluorinated carbons, and hydro fluorocarbons. (GHGGHGAny gas that absorbs infrared radiation in the atmosphere. Greenhouse gases include, carbon dioxide, methane, nitrous oxide, ozone, chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride.) in the atmosphere.
• GHGs trap heat in the atmosphere in the same way that heat is trapped in a horticultural greenhouse.
• Healthy, properly functioning ecosystemecosystemAll living things and nonliving things in an area, as well as the interactions between them.s, and natural resources such as soils, oceans and vegetation, can reduce or stabilize this rate of change through the long-term capture and storage of carbon. This process is known as carbon sequestrationcarbon sequestrationThe uptake and storage of carbon. Trees and plants, for example, absorb carbon dioxide, release the oxygen and store the carbon. Fossil fuels were at one time biomass and continue to store the carbon until burned. See carbon sinks..
• Sequestering atmospheric CO₂ in natural resources called sinks reduces the amount of CO₂ that is available to heat the atmosphere and potentially increase climate instability. 
• The Intergovernmental Panel on Climate Change (IPCC) estimates that the world's oceans have taken up 500 gigatons (Gt) of atmospheric CO₂ out of 1300 Gt CO₂ total human-caused emissions in the past 200 years¹.
• Along with soils and oceans, both below-ground (e.g., roots) and above-ground (e.g., leaves) vegetation store carbon (average of 53.5 tons of carbon per hectare for U.S. forests)².
• On a smaller scale, vegetation can mitigate climate variability and extremes by creating local micro-climates through shading and increased humidity, producing a more favorable environment for humans and wildlife.
• By storing carbon and modifying local climate conditions, our natural resources provide a means to stabilize rapidly changing climate conditions.

Stressors and drivers of change

• Many human activities such as transportation, energy production, and industrial processes emit GHGs into the atmosphere, which contribute to changing climate conditions.
• Increases in the atmospheric concentrations of both long-lived (e.g., CO₂, methane, nitrous oxide) and short-lived (e.g., ozone) GHGs have resulted in rapid changes in patterns of climatological mean conditions and variability.
• In addition to GHG emissions, land use patterns can be important drivers of climatic changes. Urbanization and increases in urban sprawlsprawlLand development that is built away from urban areas and existing town centers, creating large areas of relatively low-density residential and commercial development. development can increase vehicle miles traveled and GHG emissions from transportation, accounting for approximately 27 percent of total U.S. GHG emissions in 2010³. Urbanization also affects climate on local and larger scales by contributing to the Urban Heat Island effectUrban Heat Island effectThe urban heat island effect is a measurable increase in ambient urban air temperatures resulting primarily from the replacement of vegetation with buildings, roads, and other heat-absorbing infrastructure. The heat island effect can result in significant temperature differences between rural and urban areas.. 
• Increasing demands on food and biofuel in response to growing populations have led to increased agricultural land use and more intensive land management. Agricultural activities, such as fertilizer application and tillage, can result in the emission of nitrous oxide, and livestock produce large amounts of methane, causing agriculture to account for approximately 7 percent of total U.S. GHG emissions⁴ .
• The removal of trees or forests eliminates the carbon sequestration provided by those trees.
• However, not all land use changes contribute to GHG emissions and climate change. Over the past several decades in the U.S., land use and forestry activities have resulted in more removal of CO₂ from the atmosphere than emissions, offsetting roughly 15 percent of total U.S. GHG emissions in 2010⁵.

Health impacts and benefits

• Climate stabilization is important for the safety and security of Earth's species.
• Ecosystem protection, management, and carbon sequestration strategies help slow the current rate of changing climate averages and variability, buffering humans from the negative aspects of such change. This buffer also provides additional time to develop the technology needed to take advantage of the potentially positive aspects of such climatic changes. 
• In the near term, for instance, trees and other vegetation can help mitigate heat-related hazards by providing local cooling and reducing indoor temperatures through shading.
• Local temperature reduction may decrease hospital admissions and mortality due to heat stroke and other heat-related illnesses.
• Careful use and management of vegetation can also regulate the flow of water, and in some cases, act as a barrier from physical damage, protecting people from property loss.
• Sea-level change in response to climate warming is a potential threat along the Mid-Atlantic and portions of the Gulf Coast⁶. Slowing the rate of sea-level rise could help maintain the quality of drinking water supplies by reducing the rate of salt water intrusionsalt water intrusionDisplacement of fresh or ground water by the advance of salt water due to its greater density, usually in coastal and estuarine areas. into aquifers and the upstream movement of salt-wedges in rivers and streams.
• Slowing sea-level rise through carbon sequestration could also provide additional time to move water supply infrastructure and treatment facilities, or to develop alternative treatment technologies.
• In the longer term, increasing the stores of carbon in soil is one way to increase soil fertility and productivity. By slowing the rate of change, plant breeders have the opportunity to develop new commercial crop varieties that can flourish under these new climate patterns.
• Natural plant species have evolved and adapted to a slowly changing climate, but they can be severely challenged by more rapidly changing environmental conditions. Species that are highly adapted to certain local environments may have particular difficulty adapting to such change. However, slowing the rate of changing patterns of averages and variability offers the opportunity for many species in various locations to maintain their current levels of biodiversity through adaptation and migration to different areas, either within or outside their original ranges.
• Encouraging a less rapidly changing climate helps maintain stability in biodiversity, which underpins all services that Earth's ecosystems provide. 
• For more information on the health benefits of mitigating heat hazards, explore the Heat Hazard Mitigation portion of the Eco-Health Relationship Browser.

References 

1. IPCC. Special report on carbon dioxide capture and storage: CH 6 ExitAccessed March 2013.
2. Nowak D J and D E Crane. 2002. Carbon storage and sequestration by urban trees in the USA. Environmental Pollution, 116 (3): p 381-9.
3. EPA. GHG emissions: Transportation. Accessed March 2013.
4. EPA. GHG emission: Agriculture. Accessed June 2015.
5. EPA. GHG emissions: Land use change. Accessed March 2013.
6. EPA. Climate change: Indicators. Accessed June 2015.