Heavy rains impact wildlife, demonstrate value of wetlands

CAPE GIRARDEAU, Mo. -- While many wait expectantly for the rainy season to end, biologists know heavy rains such as this week’s weather in the bottomlands of southeast Missouri recharge wetlands by bringing new water into the system. Some conservation areas that tend to be affected by heavy rains in southeast Missouri include Ten Mile Pond, Swift Ditch Access, Seven Island CA, Donaldson Point, Wolf Bayou and Black Island. Specifically, two wetland pools in the Bradford Unit of Black Island Conservation Area (CA) are recharged as they store flood waters from the Mississippi River when it rises.

Additionally, the vegetation on bottomland conservation areas tends to slow the movement of water across the landscape, according to Private Lands Conservationist, Tim Kavan. This reduces scours and washouts and reduces sedimentation.

“Most all of the Conservation Areas that occur along the Mississippi River have the capacity to hold lots of water,” Kavan said. “They are tiny examples of how the whole region used to function. They’re capable of handling heavy rain events because that is how wetlands function.”

Wetland Ecologist Frank Nelson said although people think about heavy rain and flooding events in the spring, the flooding and drying dynamics of wetlands are typically ongoing seasonal events. As river levels rise in the spring and rain falls, low lying areas flood. As summer progresses, temperatures and evaporation increase and rainfall is less frequent, which allows flood waters to recede and low lying areas to dry out.

“This wet and dry cycle allows for these areas to have water storage capacity the following year,” Nelson said, adding that wetland plants are adapted to wet conditions and respond to them.

“Slow and steady rain irrigates plants and encourages growth,” Nelson said.

As they grow, wetland plants and trees often function as hydraulic pumps in the growing season, he said. Their roots adapt to take advantage of soggy soils, pump the water out of the ground and turn it into above ground growth and oxygen. This way, wetland plants provide an extra water storage capacity between the below and above-ground storage capacity. Although surface water storage capacity is what comes to mind during rain events, Nelson said it’s important to remember that water is also stored underground.

“Spaces between soil particles and plant matter act like the holes of a sponge and can soak up flood water,” Nelson said. “Over time, water can percolate lower into the groundwater table or deeper into the local aquifer.”

This ability to store flood water, is one reason ecologists and wildlife biologists tout the value of wetlands, but wetlands and rainfall are equally valuable to wildlife.

“Reptiles and amphibians, like the Illinois Chorus Frog and Eastern Spadefoot toad, use new wetlands to lay eggs, while crayfish burrow new homes in the fresh mud,” Kavan said.

The effects of rainfall on wildlife are numerous. Migrating shorebirds and wading birds use the newly flooded habitats to feed on aquatic species they can find there. Additionally, many fish spawn as rivers and water temperatures rise in the spring.

Timely spring rains help a variety of plants to grow and they make wetland habitats available to wildlife seeking forage, nesting opportunities, escape cover, and rest depending on the season. However, too much rain can create havoc on ground nesting birds such as wild turkey and bobwhite quail, Kavan said, adding there can also be negative effects of heavy rainfall for the public that seek access to the areas.

“Extended exposure to wind and waves can have a direct impact on roads and levees which often serve as access for recreation on these areas,” he said.

Extended flooding can limit public access to bottomland conservation areas due to muddy roads and high river stages. Despite these difficulties, opportunities are often still available on foot or by boat.

“In some rare cases, entire conservation areas may be closed during flood events to reduce stress on wildlife from extreme conditions and to protect area infrastructure from experiencing further damage,” Kavan said. “To avoid a surprise, we encourage the public to be proactive and either check online or call ahead if they think an area may be closed due to flooding.”

Visitors can look for closures on the Conservation Area Atlas at mdc.mo.gov or call the Southeast Regional Office at 573/290-5730 to check public access availability throughout the spring season.