We’ve talked about the first two pillars of tree farming: recreation and wood. Today, let’s explore water, the third beneficial product of a tree farm.
Trees, similar to natural sponges, collect and filter rainfall and release it slowly into streams and rivers. They are the most effective land cover for maintaining healthy water quality. In one single growing season, a 100-foot tree can take in 11,000 gallons of water from the soil (fs.usda.gov). After the tree drinks up the water through its hair-fine roots, it carries it all the way through its trunk, up to its leaves and releases it back into the air as oxygen and vapor. Oxygen is also produced from capture of atmospheric CO2, with carbon sequestered in roots and wood. Here, in Maryland, we’re lucky to have an abundance of creeks, rivers and the Chesapeake Bay to provide each of us with the 100 gallons of water required to support the average American each day — not to mention what natural ecosystems and wildlife need. Continued deforestation — our state was once covered by forests — and extreme weather patterns have created a serious stormwater runoff problem.
The runoff problem is two-fold. On one side, we have soil erosion, where our valuable topsoil literally washes into streams, eventually ending up in our oceans due to increasingly strong and frequent rainfalls. Soil erosion complicates life for all flora and fauna and can even cause food insecurity. Trees can help mitigate the impact of storms with their leafy canopy, which slows rainfall so it either evaporates or is dribbled more slowly onto land surface. This allows the water to penetrate the soil instead of washing it away. Root systems, in addition, take up water and condition the soil to promote infiltration and reduce runoff. Clearly, trees play an enormously important role in any stormwater management plan.
On the other side, we have stormwater pollution. This refers to the rainwater that washes over parking lots, streets and lawns and picks up fertilizer, oils and animal waste as it washes into rivers and streams — all of which eventually flows into the Chesapeake Bay and the Atlantic Ocean. In our county, we also need to consider agricultural pesticides and fertilizers in addition to poultry or cattle farm waste. The problem with stormwater pollution is that excess nitrogen, phosphorus and sediments can cause an overgrowth of algae, which blocks sunlight from animals and plants that live in deeper waters. The algae’s subsequent decomposition then depletes dissolved oxygen necessary for all aquatic life.
Despite the growing concern of stormwater runoff in our area, Maryland is regressing in its efforts to mitigate stormwater pollution. According to Abel Russ with the Environmental Integrity Project, mitigation plans have collapsed to less than 10 percent of what they once were, both in the pollution targets and in the implementation of control strategies like rain gardens. The same report urges governments, from federal to municipal levels, to invest in stronger stormwater projects and to update rainfall patterns to account for climate change instead of relying on historical data.
Some of the best strategies to counter the runoff pollution and soil erosion from heavy rainfall include planting rain gardens in cities to absorb runoff and filter water before it enters our streams. In the process, these gardens provide respite from urban heat islands, a wildlife refuge and recreational opportunities. In rural areas, we must protect our remaining watersheds. Remote sensing analysis estimates that Frederick County has nearly 100,000 acres devoted to lawn cover — that’s nearly a quarter of our county contributing to stormwater runoff troubles! Planting just a fraction of this acreage with trees would have significant benefit to water quality. In addition, we should plant riparian buffers around wetlands and creeks. Riparian buffer areas, based on Frederick County code, should be a minimum of 100 feet wide on each side of the stream for moderate slopes, and up to 175 feet for steep slopes, planted with native trees and vegetation to avoid soil erosion and to filter the runoff waters. Properly established riparian zone vegetation will remove up to 90 percent of unused nitrogen leaving the fields (data from USDA) and works best when incorporated with conservation tillage, nutrient management and prescribed grazing. Having a buffer of forestland around waterways also helps recharge the water table and keeps the temperature of the water lower, allowing certain fish like trout to spawn.
Remember Jan and Dave Barrow’s tree farm from the first installment of our miniseries? They planted 2,800 seedlings on a flood plain and improved their riparian forest. In doing so, they purified their creek’s water and have restocked it with trout, making it an ideal fishing spot. No wonder their tree farm is popular.
Stay tuned for the fourth and final installment of our mini-series on tree farms as we discuss the benefits of trees to wildlife in the next Green section. Please visit frederick.forestryboard.org anytime for more information on tree farms.