Many people advise that while the best time to plant a tree was 20 years ago, the second best time to plant a tree is today. Winter weather makes it tough to follow this advice, but the off-season does provide a bit more time to plan ahead for the year to come. Extreme rain events are increasing and farmers are working to adapt to these circumstances the best that they can. Studies show that peak rainfall events are becoming more frequent throughout the US, but this is especially so in the Northeast and Midwest. These extreme precipitation events affect agricultural and forested landscapes by increasing the volume of water flowing through streams and rivers in a very short period of time, which can exacerbate field and bank erosion, as well as flooding. Both erosion and flooding can damage crops, overload infrastructure, and increase siltation in drinking water reservoirs. With soil and water erosion comes nutrient pollution, a significant threat to our stream and coastal ecosystems.
Agroforestry systems can help landowners adapt to extreme rain events and lessen their negative impacts.
Forest and tree cover can intercept rainfall, increase the amount of rain that filters through the ground, and reduce the quantity, speed, and peak flows of runoff. Riparian forest buffers with trees, shrubs, and other plants help to filter and slow the rate of water flowing from fields by trapping sediment and nutrient pollutants.
Water doesn’t run off of fields at the same rate across a landscape. Where the land is steeper, flow becomes more concentrated. Cropping practices, soils, and other factors also influence how water runs off of a field. Decision-support tools can help land managers identify riparian areas where concentrated flow from fields is likely to occur, and determine ideal sites for riparian forest buffers. Knowing where to plant buffers can allow the farmer to get the most bang for their buck to reduce erosion and enhance water quality.
One decision support tool that helps with these efforts is AgBufferBuilder, developed by the National Agroforestry Center. The AgBufferBuilder program analyzes the lay of a field to determine how much runoff will occur, and where. The program uses various inputs, such as the desired level of trapping efficiency and Geographic Information Systems (GIS) technology to recommend where and how much buffer is needed to achieve different levels of effectiveness. The program user can also compare a fixed-width buffer to a variable-width buffer, the latter of which provides the area of each buffer necessary to achieve desired results.
Farmers and technical assistance providers are using this tool to plan ahead for intense rain events and to design riparian buffers.
AgBufferBuilder has been used in a number of landscapes in the Northeast United States and Atlantic Canada, as well as other parts of the United States. Users have tested different scenarios, seeing the impacts of riparian buffers in different parts of their fields under different cropping systems. This allows users to assess the compatibility of different buffer sizes and shapes with their farming systems, as well as how those buffer scenarios would enhance water quality. This is a great activity for winter, when you can plan ahead for spring tree planting.
Riparian buffers work best as part of a system of conservation practices. In many ways, they are the last line of defense against these intense rain events. Adding more continuous living cover across the farm through agroforestry and other practices can increase the amount of water that goes into the ground instead of running off into ditches, streams, and rivers. Consider planning now for these riparian buffer benefits later.
Article by Kate MacFarland, Collaborating Scientist/Researcher, USDA Northeast Climate Hub and Agroforester, USDA Forest Service, National Agroforestry Center