Wetlands 101

Our waterways are all subject to change, both naturally and artificially. Wetlands are a great example of this. According to the US Army Corps of Engineers, an area is a wetland if it contains the following three indicators: (1) wetland plants, (2) hydric soil, (3) and water at or near the surface. It’s important to note that not all wetlands are wet year-round; seasonal cycles affect our wetlands, and it’s not uncommon to see them dry in late summer. This blog will explore what makes a wetland, what they do for the environment, and how they change over time. 

How do wetlands form? 

Typically, wetlands form one of 5 ways – or a combination of ways. 

1) Flooding of coastal lowlands. Floods can be dramatic enough to change an area’s biome, particularly when sea levels rise. Sediment deposits can also deposit plants, which take root and cultivate a marsh. 

2) River floodplains. Riparian wetlands will also form when extreme floods dump sediment on riverbanks. This sediment can change the shape and flow of the river. 

3) Glaciers. Many of our large wetlands were formed by glaciers and glacial movement. If an area with poor drainage was left with a massive chunk of ice, a wetland would form when the ice melted. 

4) People. Collective human actions can greatly impact wetlands. Restoration and conservation work to preserve wetland habitat can include creating new wetlands in approved areas. These areas are mitigated to ensure their long-term success. Construction projects can also alter drainage patterns or waterways, impacting local wetlands. In some instances, this will cause a wetland to disappear. In others, this will create a new wetland.  

5) Beavers. Our furry friends were once responsible for many ponds and wetlands due to their voracious need to build dams. These beaver dams stop or slow the flow of water, creating pools. When on a large scale, beavers can create entire wetlands. These days, we don’t have enough beavers to play an overly significant role in creating wetlands. However, as the population of beavers recovers, Kirkland beavers are once again helping to bring back wetlands. 

 

How do wetlands benefit the environment? 

1. Water Purification. Wetlands are experts at trapping sediment, excess nutrients, and heavy metals. These elements enter water through runoff. Runoff is created when rain and stormwater travels over land on its way to a body of water, where it picks up harmful materials and sediment. The soil composition of wetlands means they are able to soak up these excess nutrients, either being used by the wetland plants or converting them into less harmful chemical forms in the soil itself. 
2. Flood Protection. Almost all wetlands provide flood protection by holding excess runoff from storms. Wetlands will slow the flow of water by temporarily holding the water – acting as a sponge. Even a wetland not connected to further waterways will soak up runoff and help prevent our backyards from turning into a pool. 
3. Shoreline Stabilization. Wetlands that do connect to further waterways help protect the banks from erosion. Wetlands can act as a buffer, providing stabilization with their extensive root systems. 
4. Groundwater Recharge & Streamflow Maintenance. In this context, “recharge” means the replenishing of water through rain. The powerful wetland soil and root systems slow the water, allowing for deep infiltration. 
5. Fish and Wildlife Habitat. Wetlands provide habitat for many species, including essential breeding habitat. The conditions and cover provided by wetlands create a unique ecosystem that some species rely on. Wetlands are essential for the success of salmon and the endangered Oregon spotted frog, for example.  

Because wetlands are so diverse, not all wetlands will accomplish all these benefits. However, they all will accomplish some of these benefits. At the end of the day all wetlands benefit our environment. 

 

Why do wetland boundaries change? 

The boundaries of a wetland are vulnerable to changes in the surrounding environment. For example, removing plants from a wetland will impact the wetland’s infiltration capacity.   

Changing the depth, width, or draining the wetland can all severely impact the health of the wetland. These all create major changes to the hydrology – the distribution and movement of water.  

Changes in land use, such as development of the land or adding hard surfaces to the surrounding area, can create a challenge for the wetland. These alterations create more runoff, which can overwhelm the current biology of the wetland.  

One of the most obvious and instantaneous changes to a wetland can happen with the removal of beaver dams, creating a sudden flow to the surrounding area and any connected waterways.  

 

Climate Change 

Our changing climate impacts wetland formation, conservation, and success. Wetlands store significant amounts of carbon, making them a valuable tool in the fight against climate change. Undisturbed wetlands store nearly twice as much carbon as wetlands disturbed by human activities. However, changes in temperature, sea level, rainfall, and snowpack all affect the delicate ecosystems of our wetlands. 

As we mentioned before, some wetlands dry out seasonally. Climate change may lengthen this dry period and dry out wetlands that are rarely dry. This change would drastically impact the plant and animal life that call wetland habitats home.  

The more you know! We hope this deep dive into wetlands enhanced your knowledge about our environmental sponge. Wetlands are a dynamic and essential part of the Washington environment and, more locally, our Kirkland environment. If you’re looking to safely explore a wetland, we recommend Big Finn Hill Park, Juanita Bay Park, Neal-Landguth Wetland Park, and Yarrow Bay Wetlands.  

If reading this sparked any questions, feel free to reach out to me directly at stormwater@kirklandwa.gov. 

PROTIP – If you’re looking to soar into the world of birding, wetlands are a great place to start! These biodiverse havens create the ideal habitat for many of our native species. 

Sources: 

Washington Department of Ecology, Wetlands through the seasons 

Washington Department of Ecology, Wetlands & climate change 

Washington Department of Ecology, At Home with Wetlands 

National Park Service, How are wetlands formed? 

US Army Core of Engineers, Wetlands 

City of Kirkland, Critical Area Regulations 

Leave No Trace, The 7 Principles