By Christopher Intagliata
22 November 2016
(Scientific American) – Climate change may be partly to blame for the massive die-off of pine trees in the western U.S. But it works the other way, too: forest die-offs can alter the global climate.
"I like thinking of this as a parallel to something like El Nino." Abigail Swann, an ecological climatologist at the University of Washington. "We think these are also going to have climate impacts far away from where those forests are dying. So it's going to ricochet in other places around the globe."
To model those "ricochet" effects, Swann and her colleagues used climate simulations to wipe out forests and replace them with grasslands, in the western U.S., the Amazon, or both. They found that losing forests in one part of the globe does indeed affect climate very far away. "And that could be negative in a lot of places, it could be bad for the ecosystems, but you could come up with scenarios where it makes the conditions a little bit better." [more]
ABSTRACT: Forest loss in hotspots around the world impacts not only local climate where loss occurs, but also influences climate and vegetation in remote parts of the globe through ecoclimate teleconnections. The magnitude and mechanism of remote impacts likely depends on the location and distribution of forest loss hotspots, but the nature of these dependencies has not been investigated. We use global climate model simulations to estimate the distribution of ecologically-relevant climate changes resulting from forest loss in two hotspot regions: western North America (wNA), which is experiencing accelerated dieoff, and the Amazon basin, which is subject to high rates of deforestation. The remote climatic and ecological net effects of simultaneous forest loss in both regions differed from the combined effects of loss from the two regions simulated separately, as evident in three impacted areas. Eastern South American Gross Primary Productivity (GPP) increased due to changes in seasonal rainfall associated with Amazon forest loss and changes in temperature related to wNA forest loss. Eurasia’s GPP declined with wNA forest loss due to cooling temperatures increasing soil ice volume. Southeastern North American productivity increased with simultaneous forest loss, but declined with only wNA forest loss due to changes in VPD. Our results illustrate the need for a new generation of local-to-global scale analyses to identify potential ecoclimate teleconnections, their underlying mechanisms, and most importantly, their synergistic interactions, to predict the responses to increasing forest loss under future land use change and climate change.