Discriminating the biophysical signal from human‐induced effects on long‐term primary production dynamics. The case of Patagonia. (27th June 2021)

• Record Type: Journal Article
• Authors: Irisarri, J. Gonzalo N.; Texeira, Marcos; Oesterheld, Martín; Verón, Santiago R.; Della Nave, Facundo; Paruelo, José M.
• Is Part Of: Global change biology. Volume 27:Number 18(2021)
• Page Start: 4381
• Page End: 4391
• Publication Date: 2021-06-27
• Subjects: ENSO -- GIMMS -- NDVI -- RESTREND -- SOI; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.15733
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: The temporal trend of aboveground net primary production (ANPP) is frequently used to estimate the effect of humans on ecosystems. In water‐limited ecosystems, like most grazing areas in the world, the effect of humans act upon ANPP in combination with environmental variations. Our main objective was to quantify long‐term (1981–2012) changes of ANPP and discriminate the causes of these changes between environmental and human at a subcontinental scale, across vast areas of Patagonia. We estimated ANPP through a radiative model based on remote sensing data. Then, we evaluated the relation between ANPP and environmental interannual variations of two hierarchically related factors: El Niño Southern Oscillation (ENSO) through the Southern Oscillation Index (SOI), and precipitation. We described the effect of humans through the shape of the temporal trends of the residuals (RESTREND) of the environmental model and quantified human relative impact through the RESTREND: ANPP trend ratio. ANPP interannual variation was significantly explained by ENSO (through SOI) and precipitation in 65% of the study area. The SOI had a positive association with annual precipitation. The association between ANPP and annual precipitation was positive. RESTREND analysis was statistically significant in 92% of the area where the tested environmental model worked, representing 60% of the study area, and it was mostly negative. However, its magnitude, revealed through the RESTREND: ANPP trend ratio, was relatively mild. Our analysis revealed that most of ANPP trends were associated with climate and that even when human density is low, its incidence seems to be mainly negative. Abstract : How do climate and human signals affect primary production dynamics? Across a 150–1000 mm gradient of mean annual precipitation, we found that primary production tended to be higher under La Niña than under El Niño conditions. At the extreme arid part of the gradient, La Niña effect was mediated by higher precipitation. After controlling for the climatic signal, the human footprint on ANPP dynamics was majorly negative, but its magnitude was milder than the influence of climate.