Analyzing the subtleties of the association between forests and water

The infrastructure that brings drinking water to homes is an investment. For millions of people, forests are part of the system behind their taps. Many forested watersheds may be lost over the coming decades, lowering water quality and increasing water treatment costs, a new study published in the journal Nature shows. macroenvironmental science.

The research team focused on the association of forests with water in the southern United States, which is a complex, heterogeneous region and, unfortunately, an ideal place to study forest loss and deterioration in water quality. More than 80% of the southern forests are privately owned, and the population is growing. More Southern forests have been lost to development than anywhere else in the United States. When forests are replaced by parking lots, neighborhoods, and other development, the loss is essentially irreversible.

“To our knowledge, this is the first study to combine water quality data, land cover projections, and information about public water systems on a large scale,” says Peter Caldwell, a Forest Service researcher and lead author of the new study.

“Our research team includes economists who will relate water quality to water treatment costs,” Caldwell says. “This kind of research could one day inform programs that compensate private forest land owners for the ecosystem services that forest watersheds provide.”

“We examined small watersheds across a wide area,” says Katherine Martin, a researcher at North Carolina State University and co-author of the study. “From Virginia to Texas, and across different forest types, soils, topography, and aquatic climates, our results confirm that forests are important to water quality.”

Runoff water in forest lands generally contains lower concentrations of nitrogen, phosphorus, and suspended sediment than water leaving any other type of land, the study found.

But there are nuances in the relationship between clean water and forests. Some forested watersheds can have lower water quality, possibly due to the type of soil and rock in the watershed, or sediment erosion in the stream channel. “These and other factors can make quantifying the benefits of forests difficult,” Caldwell says.

However, the study notes that the loss of forests to any other land use will likely lead to a decrease in water quality. For example, developing just 1% of upstream forests can lead to a 0.4% increase in the concentration of suspended sediment in the water, on average.

Municipalities that draw water directly from rivers are at greater risk of reduced water quality, now and in the future. Water drawn from a river rather than actually a reservoir tends to undergo further treatment before the water is fit to drink. Municipalities that draw water from smaller watersheds also face greater risks, since any forest lost in a small watershed can account for a larger proportion of its area.

Protecting forest watersheds can help protect drinking water supplies in the future. In general, the more forested area upstream of an intake facility, the better the water quality.

The new study is related to large body of research On how people rely on forested watersheds for drinking water.

The research team also works with alliances such as Keeping Forests. “We are bringing scientists, business leaders and conservation experts together to develop market-based approaches to support private landowners,” says Laura Calandrella, executive director of Keeping Forests. “By highlighting the economic and ecological benefits of Southern forests, we enable people to conserve forests as forests.”