Wetlands are vulnerable to climate change
Because of their position where land and waters meet, wetlands are at risk of damage from climate change. Effects of climate change on wetlands may include:
- Loss of carbon stored in soil
- Changes in soil structure
- More frequent drying or flooding
- Changes in plant or animal communities
- Saltwater intrusion to freshwater coastal wetlands
- Changes in timing and amount of water available to wetlands fed by snow melt.1
Most of the carbon stored in wetlands is in the soil, where carbon cycling and microbial processes take a long time to develop. For example, the organic soil in peatlands can take thousands of years to develop- it can take up to 250 years for just one inch of peat to accumulate.2 Disturbance of those systems can result in loss of the carbon stored in those soils to the atmosphere.3 It is estimated that oxidation of disturbed organic soil contributes a substantial amount of CO2 to the atmosphere.1 Undisturbed wetlands store nearly twice as much carbon as wetlands disturbed by human activities.4 Warmer temperatures and changes in precipitation can also increase the loss of carbon stored in wetland soils.1 The combination of wetland disturbance from human activities and changes in climate may have greater impacts on wetland functions than either stressor would alone.1
Wetlands that rarely dry out are expected to shift to more frequent drying in some areas, and wetlands that currently are frequently dry may be lost in some areas. In other areas where precipitation is expected to increase or the timing is expected to change, wetlands that occasionally dry out may become wetter.5
Wetlands in some areas may be at greater risk. For example, montane wetlands are expected to be affected by higher temperatures, less snow pack, and earlier snow melt, resulting in a loss of more seasonal wetlands and habitats suitable for amphibians and wetland invertebrates.6 In addition to changes in temperature and precipitation, coastal wetlands will be impacted by sea level rise. In the Puget Sound region, sea level was estimated to rise gradually by 15 to 54 inches.7 A more recent effort to estimate sea level rise along Washington's coast includes changes in land elevation to generate relative sea level rise projections for different carbon emissions scenarios and based on the probability of occurrence.8 For example, they estimated a 50 percent chance of sea level to rise 2.7 ft in Olympia under a high carbon emission scenario, with a range of 2.0 ft -3.4 ft most likely (83-17% chance).9 This rise in sea level can result in saltwater intrusion to freshwater wetlands and water depths too deep for coastal wetland plants to survive. In areas where coastal wetlands are not able to move inland as the water rises, they may disappear.
The changes to wetlands that may happen with climate change can alter water quality, water quantity, and habitat functions.1, 10, 11 The response of individual wetlands to climate change will depend on:
- Exposure to altered climate conditions.
- Sensitivity to those changes.
- Potential impacts from exposure and sensitivity.
- Capacity to adapt.12