Widespread decline of Congo rainforest greenness in the past decade.
Tropical forests are global epicentres of biodiversity and important modulators of climate change, and are mainly constrained by rainfall patterns. The severe short-term droughts that occurred recently in Amazonia have drawn attention to the vulnerability of tropical forests to climatic disturbances. The central African rainforests, the second-largest on Earth, have experienced a long-term drying trend whose impacts on vegetation dynamics remain mostly unknown because in situ observations are very limited. The Congolese forest, with its drier conditions and higher percentage of semi-evergreen trees, may be more tolerant to short-term rainfall reduction than are wetter tropical forests, but for a long-term drought there may be critical thresholds of water availability below which higher-biomass, closed-canopy forests transition to more open, lower-biomass forests. Here we present observational evidence for a widespread decline in forest greenness over the past decade based on analyses of satellite data (optical, thermal, microwave and gravity) from several independent sensors over the Congo basin. This decline in vegetation greenness, particularly in the northern Congolese forest, is generally consistent with decreases in rainfall, terrestrial water storage, water content in aboveground woody and leaf biomass, and the canopy backscatter anomaly caused by changes in structure and moisture in upper forest layers. It is also consistent with increases in photosynthetically active radiation and land surface temperature. These multiple lines of evidence indicate that this large-scale vegetation browning, or loss of photosynthetic capacity, may be partially attributable to the long-term drying trend. Our results suggest that a continued gradual decline of photosynthetic capacity and moisture content driven by the persistent drying trend could alter the composition and structure of the Congolese forest to favour the spread of drought-tolerant species.
Department of Atmospheric and Environmental Sciences, University at Albany, State University of New York (SUNY), Albany, New York 12222, USA.
Liming
L
Zhou
I. M. Systems Group (IMSG), National Oceanic and Atmospheric Administration/National Environmental Satellite, Data, and Information Service/The Center for Satellite Applications and Research (NOAA/NESDIS/STAR), 5830 University Research Court, College Park, Maryland 20740, USA.
Yuhong
Y
Tian
Department of Earth and Environment, Boston University, Boston, Massachusetts 02215, USA.
Ranga B
RB
Myneni
Laboratoire des Sciences du Climat et de l'Environnement (LSCE), CEA-CNRS-UVSQ, 91191 Gif sur Yvette Cedex, France.
Philippe
P
Ciais
Jet Propulsion Laboratory, Pasadena, California 91109, USA.
Sassan
S
Saatchi
ARC Centre of Excellence for Climate Systems Science & Climate Change Research Centre, University of New South Wales, Sydney, New South Wales 2052, Australia.
Yi Y
YY
Liu
Department of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.
Shilong
S
Piao
Key Laboratory of Meteorological Disaster, Ministry of Education, Nanjing University of Information Science and Technology, Nanjing 210044, China.
Haishan
H
Chen
NASA Goddard Space Flight Center, Code 619, Greenbelt, Maryland 20771, USA.
Eric F
EF
Vermote
1] Department of Geography, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 29599, USA [2] School of Forestry and Landscape Architecture, Anhui Agricultural University, Hefei, Anhui 230036, China.
Conghe
C
Song
Institute for the Environment, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 29599, USA.
Taehee
T
Hwang
D000064:Acclimatization; D044822:Biodiversity; D018533:Biomass; D002734:Chlorophyll / Q000032:analysis / Q000378:metabolism; D057231:Climate Change / Q000706:statistics & numerical data*; D003223:Congo; D055864:Droughts / Q000706:statistics & numerical data; D010788:Photosynthesis; D018515:Plant Leaves / Q000254:growth & development* / Q000378:metabolism; D011891:Rain; D063809:Satellite Imagery; D012621:Seasons; D013696:Temperature; D013997:Time Factors; D014197:Trees / Q000254:growth & development* / Q000378:metabolism; D014329:Tropical Climate; D014867:Water / Q000032:analysis / Q000378:metabolism; D014934:Wood / Q000254:growth & development / Q000378:metabolism
D014867:Water; D002734:Chlorophyll