Hotter and drier climate made the Mediterranean Europe and Northern Africa (MENA) region a shrubbier landscape

Wei Fang and Gabriella Lam, Department of Biology, Pace University, New York, NY, Chuixiang Yi, School of Earth and Environment, Queens College of City University of New York, Flushing, NY, Deliang Chen, Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden

Background/Question/Methods
A shift to warmer temperatures has left the Mediterranean Europe and Northern Africa (MENA) region more vulnerable to drought and land degradation. We used LAI deficit and GPP deficit, the difference between actual and historical-maximum values, to describe vegetation structural and functional dynamics and consequential landcover change in response to climate variability during 2001-2019 in the area (20°W-45°E, 20°N-45°N).
Results/Conclusions
We found that (1) the directions of influence (signs of correlation coefficients) of climate indices over LAI and GPP deficits were negative for temperature and dryness index, positive for precipitation and Temperature-Precipitation (TP) Index, and unidentifiable for Standardized Precipitation/Evapotranspiration Index (SPEI). (2) The vegetation responses varied significantly among eight landcover types with the following ranked importance: forests, savannas, a mosaic of cropland and natural vegetation (CNV), croplands, permanent wetlands, urban land, grasslands, and shrublands, each with distinctive yet overlapping signatures over the spectrums of the climate conditions considered. (3) Forests, occupying the coolest and wettest niche of the MENA region, showed the strongest response to severe drought events, with an immediate lag of 1-3 years and a long-term legacy effect of 10 years. (4) The total areas of savannas and CNV mosaics in MENA increased by 394,994 km2 and 404,592 km2 respectively while that of forests decreased by 33,091 km2 despite of the fertilizer effect of elevated ambient CO2. Shrublands, occupying the hottest and driest niche of MENA, extended by 287,134 km2 while grasslands and croplands reduced by 490,644 km2 and 225,263 km2. The area of permanent wetlands increased by 49,192 km2 due to sea-level rise, and that of urban land increased by 39,570 km2 due to human land use. A net total of 57,649 km2 of barren land became vegetated over the years. With warmer temperature and more extended period of drought, MENA has evolved towards a shrubbier landscape.