Forest resilience has declined throughout much of the tropical and temperate regions globally since 2020, with increases in resilience in boreal regions.
Forest resilience to changing climate is suspected to be changing in many regions around the world, based on many independent forms of data. However, no global study has examined changes in forest resilience over time, thus we are unaware of both the trends and spatial demographics of any changes in forest resilience. This study examined the global patterns of forest resilience, indexed as the dTAC of NDVI (e.g. canopy greenness) towards or away from a tipping point after which disturbance is highly likely. This study found declining forest resilience in tropical and temperate biomes, and an increase in forest resilience in the boreal biome. There was no influence of forest management on the trends, indicating that changes in resilience were driven by regional-scale changes in water availability and temperature.
Recent observations of increasing tree mortality from a variety of disturbances have raised concern over the global resilience of forests to changing climate. Before this study, we did not know the global distribution of forest resilience to disturbance, the change in forest resilience due to climate drivers, nor did we have the ability to predict these disturbances. This study suggests that a large fraction of the tropical and temperate zones will experience increasing disturbance in the near term, with a large impact on the terrestrial carbon sink.
We used remotely sensed estimates of kNDVI (canopy greenness) at the global scale to quantify changes in NDVI from 2000-2020. The response of dTAC was particularly strong over time, with divergent patterns between the tropics and temperate biomes, where there was a decline in resilience, to the boreal zone, where there was an increase in resilience. This paper revealed that ~23% of undisturbed forests globally have reached a tipping point by which disturbance is likely imminent without a rapid change in climate. Because this represents a large amount of carbon uptake and storage globally, and particularly due to the large impact of tropical forest loss on the global carbon budget, these results are of particular concern.
Figure 1a. The change in temporal autocorrelation (dTAC) of the kernel normalized difference vegetation index (kNDVI) over 2000-2020. Positive values indicate slowing down of physiological processes, or a decline in resilience, towards a threshold for a tipping point i.e. disturbance. Negative values indicate the opposite, or an increase in resilience. Tropical and temperate regions exhibit significant trends towards decreasing resilience, with notable regional variability, while boreal regions show increased resilience. Figure 1b. the data from 1a binned as a function of climatological temperature and precipitation. The color scheme is as in 1a. Significant changes in dTAC over time are indicated as solid dots.
Principal Investigator: Giovanni Forzieri, firstname.lastname@example.org
Program Manager: Dan Stover. U.S. Department of Energy, Biological and Environmental Research (SC-33), Environmental System Science, email@example.com
This study was funded by the Exploratory Project FOREST@RISK of the European Commission, Joint Research Centre. N.G.M. was supported by the Department of Energy’s project Next Generation Ecosystem Experiment-Tropics.
Forzieri, G., Dakos, V., McDowell, N.G., Ramdane, A. and Cescatti, A., 2022. Emerging signals of declining forest resilience under climate change. Nature, pp.1-6. https://doi.org/10.1038/s41586-022-04959-9