Global environmental change is rapidly altering the dynamics of terrestrial vegetation, with consequences for the functioning of the Earth system and provision of ecosystem services1, 2. Yet how global vegetation is responding to the changing environment is not well established. Here we use three long-term satellite leaf area index (LAI) records and ten global ecosystem models to investigate four key drivers of LAI trends during 1982–2009. We show a persistent and widespread increase of growing season integrated LAI (greening) over 25% to 50% of the global vegetated area, whereas less than 4% of the globe shows decreasing LAI (browning). Factorial simulations with multiple global ecosystem models suggest that CO2 fertilization effects explain 70% of the observed greening trend, followed by nitrogen deposition (9%), climate change (8%) and land cover change (LCC) (4%). CO2 fertilization effects explain most of the greening trends in the tropics, whereas climate change resulted in greening of the high latitudes and the Tibetan Plateau. LCC contributed most to the regional greening observed in southeast China and the eastern United States. The regional effects of unexplained factors suggest that the next generation of ecosystem models will need to explore the impacts of forest demography, differences in regional management intensities for cropland and pastures, and other emerging productivity constraints such as phosphorus availability.
At a glance
- The challenge to keep global warming below 2°. Nature Clim. Change 3, 4–6 (2013). et al.
- 2013). et al. in Climate Change 2013: The Physical Science Basis (eds Stocker, T. F. et al.) Ch. 6 (IPCC, Cambridge Univ. Press,
- Increased plant growth in the northern high latitudes from 1981 to 1991. Nature 386, 698–702 (1997). , , , &
- A large and persistent carbon sink in the world’s forests. Science 333, 988–993 (2011). et al.
- Temperature and vegetation seasonality diminishment over northern lands. Nature Clim. Change 3, 581–586 (2013). et al.
- Analysis of trends in fused AVHRR and MODIS NDVI data for 1982–2006: indication for a CO2 fertilization effect in global vegetation. Glob. Biogeochem. Cycles 27, 318–330 (2013).
- Global latitudinal-asymmetric vegetation growth trends and their driving mechanisms: 1982–2009. Remote Sens. 5, 1484–1497 (2013). et al.
- Detection and attribution of vegetation greening trend in China over the last 30 years. Glob. Change Biol. 21, 1601–1609 (2015). et al.
- A two-fold increase of carbon cycle sensitivity to tropical temperature variations. Nature 506, 212–215 (2014). et al.
- Climate change, deforestation, and the fate of the Amazon. Science 319, 169–172 (2008). et al.
- Reduced streamflow in water-stressed climates consistent with CO2 effects on vegetation. Nature Clim. Change 6, 75–78 (2015). et al.
- Evaluation of terrestrial carbon cycle models for their response to climate variability and to CO2 trends. Glob. Change Biol. 19, 2117–2132 (2013). et al.
- Checking for model consistency in optimal fingerprinting. Clim. Dynam. 15, 419–434 (1999). &
- Forest response to elevated CO2 is conserved across a broad range of productivity. Proc. Natl Acad. Sci. USA 102, 18052–18056 (2005). et al.
- Effect of increasing CO2 on the terrestrial carbon cycle. Proc. Natl Acad. Sci. USA 112, 436–441 (2015). , &
- Nitrogen cycles: past, present, and future. Biogeochemistry 70, 153–226 (2004). et al.
- Impact of CO2 fertilization on maximum foliage cover across the globe’s warm, arid environments. Geophys. Res. Lett. 40, 3031–3035 (2013). , , &
- Stomatal conductance correlates with photosynthetic capacity. Nature 282, 424–426 (1979). , &
- Determination of deforestation rates of the world’s humid tropical forests. Science 297, 999–1002 (2002). et al.
- Primary forests are irreplaceable for sustaining tropical biodiversity. Nature 478, 378–381 (2011). et al.
- Nitrogen limitation of net primary productivity in terrestrial ecosystems is globally distributed. Ecology 89, 371–379 (2008). &
- The human footprint in the carbon cycle of temperate and boreal forests. Nature 447, 848–850 (2007). et al.
- Global potential of biospheric carbon management for climate mitigation. Nature Commun. 5, 5282 (2014). &
- Nitrogen deposition and its contribution to nitrogen cycling and associated soil processes. New Phytol. 139, 49–58 (1998). et al.
- Nitrogen deposition onto the United States and western Europe: synthesis of observations and models. Ecol. Appl. 15, 38–57 (2005). , , &
- High-resolution global maps of 21st-century forest cover change. Science 342, 850–853 (2013). et al.
- Human land-use practices lead to global long-term increases in photosynthetic capacity. Remote Sens. 6, 5717–5731 (2014). et al.
- Development and validation of a global database of lakes, reservoirs and wetlands. J. Hydrol. 296, 1–22 (2004). &
- Global fire emissions and the contribution of deforestation, savanna, forest, agricultural, and peat fires (1997–2009). Atmos. Chem. Phys. 10, 11707–11735 (2010). et al.
- Global data sets of vegetation leaf area index (LAI)3g and fraction of photosynthetically active radiation (FPAR)3g derived from global inventory modeling and mapping studies (GIMMS) normalized difference vegetation index (NDVI3g) for the period 1981 to 2011. Remote Sens. 5, 927–948 (2013). et al.
- Developing a global data record of daily landscape freeze/thaw status using satellite passive microwave remote sensing. IEEE Trans. Geosci. Remote Sensing 49, 949–960 (2011). , , &
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