Old growth standing guard A forest is a complex ecosystem, interacting with natural and anthropogenic forces in diverse ways. In the face of climate change, healthy, mature forests are some of the most resilient ecosystems on earth, providing crucial services and buffering against the worst effects of warmer temperatures, all while continuing to pull carbon out of the atmosphere. Carbon Although younger forests sequester carbon at faster rates, older forests store more accumulated carbon in the wood and bark of trees, as well as continue to stow away carbon beneath the ground in plant roots and soils. Fire Mature forests are often more resiliant to large disturbances like fires. Older, more established trees—often having thick bark—are less likely to be killed in a blaze and a healthy forest can regenerate much more quickly than one that is already degraded. In the boreal region, where forests are adapted to fire, an area of burned forest regenerates quickly as seeds from nearby mature trees drop and sprout in the fertile ground. Water and temperature Mature forests also provide important ecosystem services, especially the regulation of temperature and the filtration of water. Through the process of evapotranspiration, forests transport water vapor to the atmosphere, causing regional cooling, and preventing drought and vegetation dry-out that could make an area susceptible to fire or disease. An established forest ecosystem is also a water treatment plant responsible for filtering out pollution from the watershed. Studies have shown even a small strip of forest along a body of water—called a riparian buffer—can prevent excess nutrient and sediment runoff from damaging the aquatic ecosystem. How old is mature? What defines a “mature forest” is up for debate—age, tree diameter, and ecological stage all play a role in what makes a forest mature. One recent study led by researchers at Woodwell Climate assessed the maturity of 13 national forests in the United States using a combination of tree diameter and a metric called Culmination of Net Primary Productivity (CNPP), or the age at which tree canopy closure reaches 100% for a tree species.
map by Christina Shintani 14
Climate Science for Change
Summer 2023
