Urban forest patch cover across Asia over the last decade: Call for green innovation

Cities globally are facing multiple urban challenges (e.g., air pollution, heat island, biodiversity loss, runoff), prompting a growing recognition among local authorities of the necessity to integrate green infrastructure into urban planning. While the greening of cities has been well documented over the past two decades worldwide, no comprehensive assessment of tree cover trends has been conducted across the Asian continent. Here, we aimed at assessing trends in urban forest patch cover between 2007 and 2019 (Mann-Kendall test) covering 3957 urban centers across Asia, with more than 50,000 inhabitants, at a high-resolution (∼25m-pixel estimates). According to the Food and Agriculture Organization forest criteria (trees >5m height, >10% canopy cover, ≥0.5 ha contiguous patches), the average forest patch cover was 9.5% in 3957 urban centers over 2007-2019 (median: 5.6%) and decreased by 0.07%-point annually (median: +0.08%-point per year) with ∼61% of urban centers showing greener coverage. Most urban centers (∼80%) exhibited a trend ranging from - 1 to + 1%-point per year. Greener urban centers were mainly observed in North, Central, and Southeast Asia, while East Asia experienced decreases in large-block urban forest patches. In 2019, less than 1% of the total population across 3957 urban centers lived in urban centers with an average forest patch cover over 30%. The median forest patch cover declines with increasing population, from ∼5.7% in small urban areas (population <200,000) exhibiting a significant increase (median: +0.10%-point per year) to ∼4.7% in large metropolitan areas (population ≥1.5 million) exhibiting a decrease (median: - 0.04%-point per year). Innovative greening policies are needed to lower inequalities in citizens' exposure to green spaces for sustainable, liveable and healthier urban centers.