Remotely sensed resilience of tropical forests

Verbesselt, J.; Umlauf, Nikolaus; Hirota, M.; Holmgren, M.; van Nes, E.H.; Herold, M.; Zeileis, Achim; Scheffer, M.


Recent work suggests that episodes of drought and heat can
bring forests across climate zones to a threshold for massive
tree mortality. As complex systems approach a threshold for
collapse they tend to exhibit a loss of resilience, as reflected in
declining recovery rates from perturbations. Trees may be no
exception, as at the verge of drought-induced death, trees are
found to be weakened in multiple ways, aecting their ability
to recover from stress. Here we use worldwide time series
of satellite images to show that temporal autocorrelation, an
indicator of slow recovery rates, rises steeply as mean annual
precipitation declines to levels known to be critical for tropical
forests. This implies independent support for the idea that
such forests may have a tipping point for collapse at drying
conditions. Moreover, the demonstration that reduced rates of
recovery (slowing down) may be detected from satellite data
suggests a novel way to monitor resilience of tropical forests,
as well as other ecosystems known to be vulnerable to collapse