Coastal Watershed Institute

Even better when we get beavers involved

You dug a rain garden — a shallow depression planted with native plants that captures storm runoff and lets it soak in instead of flooding your basement or overwhelming the storm drain. Within one season, a workforce moved in that you didn't plant or purchase.

Native bees — mining bees, sweat bees, cellophane bees — began nesting in the bare soil patches between plants. Over 70 percent of native bee species nest in the ground. Your rain garden's exposed soil is their apartment complex.

Green frogs and toads colonized the damp margins. They eat the mosquitoes, beetles, and slugs that the standing water attracts — converting what could have been a pest breeding ground into a predator feeding station.

Dragonflies and damselflies established territories over the temporary water. Their nymphs consume mosquito larvae underwater. Their adults patrol the airspace above. They turned your rain garden into a mosquito-free zone.

Butterflies — swallowtails, skippers, sulfurs — found the native flowers and began pollinating. They also lay eggs on the host plants you chose, producing caterpillars that feed the chickadees nesting in the hedge beside the garden.

You installed a rain garden. Nature installed a workforce. Every organism in it is performing a service you'd otherwise pay for — pollination, pest control, mosquito suppression, water filtration.

You dug a hole. They built a department.

The creek behind your neighborhood is eroding. The banks are collapsing. Mud clouds the water after every rain. The walking trail alongside it keeps washing out.

Three organisms were holding those banks together before the landscape was altered.

Tree roots — especially willows, alders, and sycamores that grow at water's edge — anchor streambank soil with root networks that extend laterally for dozens of feet. The trees you cut because they "blocked the view" or "dropped too many leaves" were the structural rebar of the bank. Without them, the soil has nothing to grip.

Beaver dams slow water velocity upstream of the dam. Slower water means less erosive force on the banks downstream. The dam also traps sediment — the same sediment that would otherwise cloud the water and smother the streambed gravel that fish and insects need to spawn.

Crayfish burrow into streambanks, creating channels that drain subsurface water and reduce the hydrostatic pressure that causes bank slumping. Their burrows look like damage. They're structural relief valves.

You cut the trees. You removed the beaver. You poisoned the crayfish with lawn runoff. The banks collapse. The trail washes out. The county spends thousands on rip-rap and gabion baskets to replace what three organisms were doing for free.