Over the past two decades, extensive forest death triggered by hot and dry climatic conditions has been documented on every continent except Antarctica. Forest mortality due to drought and heat stress is expected to increase due to climate change. Although research has focused on isolated incidents of forest mortality, little is known about the potential effects of widespread forest die-offs. A new analysis of the current literature on this topic by Carnegie’s William and Leander Anderegg is published September 9 in Nature Climate Change.
Along with co-author Jeffrey Kane of Northern Arizona University, the Andereggs examined papers dealing with different aspects of forest die-off events from studies all over the world. They divided their findings into the effects on a forest community of trees and other species; on ecosystem processes as a whole; on services forests provide to humans; and on the climate.
“This study provides a state-of-the-art overview of the many benefits forests provide to humans, from water purification to climate regulation,” said William Anderegg, “Many of these roles can be disrupted by the widespread tree mortality expected with climate change.”
They found that heat and drought, including drought-related insect infestation, can disproportionately affect some species of trees, or can hit certain ages or sizes of trees particularly hard. This can result in long-term shifts in an area’s dominant species, with the potential to trigger a transition into a different ecosystem, such as grassland. It can also impact the understory—the layer of vegetation under the treetops—as well as organisms living in the soil. More research on forest community impacts is needed, particularly on the trajectories of regrowth after forest die-off.
From an ecosystem perspective, forest die-off will also likely affect hydrological processes and nutrient cycles. Depending on the type of forest, soil moisture could be increased by the lack of tree-top interception of rainfall or decreased by evaporation due to more sun and wind exposure. Debris from fallen trees could also increase a forest’s fire risk.
Written By: PhysOrgcontinue to source article at phys.org