Abstract
Tropical forests have essential functions in global C dynamics but vulnerable to changes in land cover land use (LCLUC) and climate. The tropics of Caribbean are experiencing warming and drying climate and diverse LCLUC. However, large-scale studies to detect long-term trends of C and mechanisms behind are still rare. Using MODIS Enhanced Vegetation Index (EVI), we investigated greenness trend in the Greater Antilles Caribbean during 2000–2015, and analyzed trend of vegetation patches without LCLUC to give prominence to climate impacts. We hypothesized that night warming and heavy cloudiness would reduce EVI in this mountainous tropical region. Over the 15 years, EVI decreased significantly in Jamaica, Haiti, Dominican Republic, and Puerto Rico, but increased in Cuba partly due to its strong reforestation. Haiti had the largest decreasing trend because of continuous deforestation for charcoals. After LCLUC was excluded, EVI trend still varied greatly, decreasing in the windward but increasing in the leeward of Puerto Rico. Nighttime warming reinforced by spatially heterogeneous cloudiness was found to significantly and negatively correlate with EVI trend, and explained the spatial pattern of the latter. Although cooled daytime and increased rainfall might enhance EVI, nighttime warming dominated the climate impacts and differentiated the EVI trend.
Highlights
Climate changes could alter functions of tropical forests in global C cycles and weaken their sink capacity
We found that the average Enhanced Vegetation Index (EVI) during 2000–2015
The country-level forest change reported by World Bank showed decreased forest cover for Haiti and Jamaica, but increased for Cuba, Dominican Republic, and Puerto Rico in 2000–2012 (Supplementary Figure S1b)
Summary
Climate changes could alter functions of tropical forests in global C cycles and weaken their sink capacity. A review of drought under global warming revealed a substantial increase of global aridity since the 1970s, and climate models predicted increased aridity over most of the Americas in the 21st century[6] Both warming and drought would reduce C sequestration capability of tropical forests and likely change them from a C sink to a C source[7,8,9]. It is crucial to investigate the synergetic impacts of climate change and LCLUC (deforestation and reforestation) in order to determine the C sequestration capability of tropical forests. Diverse LCLUC, together with dense populations and economic shift between agriculture and industry, makes the tropical ecosystem in the Caribbean vulnerable to the climate change and amplifies the uncertainties in projection of the future C sink capabilities. The relative importance of climate change versus LCLUC as well as the interaction between the two drivers in vegetation greenness is rarely explicitly addressed in the literature, which weakens the conclusion of climate change impact on vegetation greenness, especially for the tropical regions with diverse LCLUC
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