It has been suggested that rainfall in the Amazon decreases if forest loss exceeds some threshold, but the specific value of this threshold remains uncertain. Here, we investigate the relationship between historical deforestation and rainfall at different geographical scales across the Southern Brazilian Amazon (SBA). We also assess impacts of deforestation policy scenarios on the region’s agriculture. Forest loss of up to 55–60% within 28 km grid cells enhances rainfall, but further deforestation reduces rainfall precipitously. This threshold is lower at larger scales (45–50% at 56 km and 25–30% at 112 km grid cells), while rainfall decreases linearly within 224 km grid cells. Widespread deforestation results in a hydrological and economic negative-sum game, because lower rainfall and agricultural productivity at larger scales outdo local gains. Under a weak governance scenario, SBA may lose 56% of its forests by 2050. Reducing deforestation prevents agricultural losses in SBA up to US$ 1 billion annually.

已经提出，如果森林损失超过某个阈值，亚马逊地区的降雨会减少，但是该阈值的具体值仍不确定。在这里，我们调查了整个巴西南部亚马逊（SBA）上不同地理尺度上的历史森林砍伐与降雨之间的关系。我们还评估了森林砍伐政策方案对本地区农业的影响。在28 km的网格单元内，森林损失高达55–60％，这会增加降雨，但是进一步的森林砍伐会急剧减少降雨。该阈值在较大范围内较低（56 km处为45–50％，112 km网格处为25–30％），而224 km网格内的降雨量线性下降。广泛的森林砍伐导致水文和经济负和博弈，因为较低的降雨量和较大规模的农业生产力超过了当地的收益。