Trees in urban areas act as carbon sinks and provide ecosystem services for residents. However, the impact of urbanization on tree coverage in South America remains poorly understood. Here, we make use of very high resolution satellite imagery to derive urban tree coverage for 882 cities in South America and developed a tree coverage impacted (TCI) coefficient to quantify the direct and indirect impacts of urbanization on urban tree canopy (UTC) coverage. The direct effect refers to the change in tree cover due to the rise in urban intensity compared to scenarios with extremely low levels of urbanization, while the indirect impact refers to the change in tree coverage resulting from human management practices and alterations in urban environments. Our study revealed the negative direct impacts and prevalent positive indirect impacts of urbanization on UTC coverage. In South America, 841 cities exhibit positive indirect impacts, while only 41 cities show negative indirect impacts. The prevalent positive indirect effects can offset approximately 48% of the direct loss of tree coverage due to increased urban intensity, with full offsets achieved in Argentinian and arid regions of South America. In addition, human activity factors play the most important role in determining the indirect effects of urbanization on UTC coverage, followed by climatic and geographic factors. These findings will help us understand the impact of urbanization on UTC coverage along the urban intensity gradient and formulate policies and strategies to promote sustainable urban development in South America.

中文翻译：

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高分辨率卫星图像揭示了城市化对南美洲城市树冠覆盖率普遍存在的积极间接影响

城市地区的树木充当碳汇，为居民提供生态系统服务。然而，人们对城市化对南美洲树木覆盖率的影响仍知之甚少。在这里，我们利用超高分辨率卫星图像得出南美洲 882 个城市的城市树木覆盖率，并开发了树木覆盖率影响 (TCI) 系数来量化城市化对城市树冠 (UTC) 覆盖率的直接和间接影响。直接影响是指与城市化水平极低的情景相比，由于城市强度的上升而导致的树木覆盖率的变化，而间接影响是指人类管理实践和城市环境变化导致的树木覆盖率的变化。我们的研究揭示了城市化对 UTC 覆盖范围的负面直接影响和普遍的积极间接影响。在南美洲，841 个城市表现出积极的间接影响，而只有 41 个城市表现出消极的间接影响。普遍存在的积极间接影响可以抵消约 48% 由于城市强度增加而造成的树木覆盖率直接损失，阿根廷和南美洲干旱地区已实现完全抵消。此外，人类活动因素在决定城市化对UTC覆盖的间接影响方面发挥着最重要的作用，其次是气候和地理因素。这些发现将帮助我们了解城市化对沿城市强度梯度的UTC覆盖范围的影响，并制定促进南美洲可持续城市发展的政策和战略。