EnviroAtlas Benefit Category: Natural Hazard Mitigation

Ecosystems help mitigate the effects of natural hazards

• Human activities can significantly impact the natural functioning of ecosystems. In particular, land managment can contribute to natural hazards such as floods and droughts by removing vegetation that helps absorb water and replacing it with impervious surfacesimpervious surfacesSurfaces such as paved streets, parking lots, and building rooftops that prevent precipitation from soaking into the ground. Different surfaces can have different degrees of imperviousness. that increase the quantity and speed of water runoff during precipitation events. 
• Land management activities can also result in the conversion or destruction of very useful water regulating habitats, such as wetlands, that are highly effective at helping to control water flow and storm surge.
• The removal of vegetation can contribute to heat hazards because trees can shade and cool areas, reducing local temperatures.
• Altering the hydrologic flow via human activities such as dam construction interrupts the overall functioning of aquatic systems by slowing water flow, trapping sediments, changing temperature, and promoting the presence of non-native and invasive speciesinvasive speciesA type of plant, animal, or other organism that does not naturally live in a certain area but has been introduced there, often by people. An invasive species can spread quickly, especially if it has no natural predators in its new home. An invasive species can hurt native species, disrupt ecosystems, and create problems for people (for example, weeds and insects that damage crops)..¹
• Invasive species may further undermine natural communities by crowding out native species in riparian areasriparian areasAreas bordering streams, lakes, rivers, and other watercourses. These areas have high water tables and support plants that require saturated soils during all or part of the year. Riparian areas include both wetland and upland zones., changing local species composition, and affecting the structural integrity of the environment.
• Not only do human activities affect the structure and function of ecosystems, but they also reduce the resiliency of these systems and their ability to cope with natural hazards and a changing climate. Changes in climate are a significant driving force in shifting weather patterns, which can result in increased severity and frequency of extreme weather events that create these natural hazards.
• Agricultural practices and increased development can contribute to a negative feedback loop by causing the removal of tree cover and subsequent effects on climate.

 Benefits of natural hazard mitigation

• Though the occurrence of extreme weather events and natural hazards is inevitable, their effects can be at least partially mitigated by the presence of natural resources and intact landscapes.
• In coastal areas, coral reefs and estuaries can limit the damaging effects of storm surges and tidal waves by acting as a physical barrier that reduces the water's height and speed². Up to 90% of the energy from wind-generated waves is absorbed by coral reefs, which helps protect adjacent ecosystems and human structures³.
• Wetland vegetation such as mangroves and salt marshes can also literally bind the shoreline together and reduce the potential for erosion. By acting as a barrier and mitigating the effects of extreme weather, healthy ecosystems help prevent the loss of properties and crops in vulnerable areas. This protection increases the safety and security of populations that may be affected by natural hazards.
• In areas where natural ecosystems have been compromised, the effects of hazards such as storm surges and floods are worsened. For instance, the effects of Hurricane Katrina in 2005 were exacerbated by the loss of the Mississippi River Delta, development, and the presence of dams - all of which compromised the effectiveness of water regulating natural resources⁴.
• By reducing the effects of flooding, natural resources help to reduce the negative health effects, such as physical injury and psychological distress, associated with these events.
• Trees and other vegetation also aid in mitigating the effects of heat-related hazards by locally cooling areas and reducing indoor temperatures through shading. This may decrease hospital admissions and mortality due to heat stroke and other heat-related illnesses.
• This vegetation also acts a sponge by intercepting, absorbing and slowing releasing water, replenishing groundwater resources and guarding against drought.
• For more information on the health benefits of hazard mitigation, explore the Water Hazard Mitigation portion of the Eco-Health Relationship Browser.

References

1. International Rivers. Environmental Impacts of Dams.  Accessed February 2013.
2. Ramsar Convention on Wetlands. 2014. Wetlands: a natural safeguard against disasters. Fact sheet.  Accessed March 2022.
3. NOAA. How do coral reefs protect lives and property?  Accessed June 2018.
4. Ramsar Convention on Wetlands. 2011. Wetland ecosystem services: Shoreline stabilization and storm protection. Accessed December 2021.