A Global Slowdown in the Enhancement of Urban Vegetation

Cities experience rapid environmental changes, and thus the vegetation change in the urban area can provide insights into how vegetation responds to future environmental change. Although previous research has reported a global rise in indirect effects (ωᵢ) of urban vegetation growth, the specific temporal patterns and changes in this growth improvement remain inadequately investigated. To address this, ωᵢ trends over the past two decades were analyzed and data-driven artificial intelligence models were developed to predict future growth under various climate scenarios in 4,983 cities worldwide. The analysis revealed that the ωᵢ exhibited a logistic increase over time, culminating in an approximate 70% enhancement by 2020. However, predictions from the six models indicate a transition to a slower, linear growth pattern moving forward, with an additional growth ranging between 16% and 30% from 2020 to 2100. This marks a stark contrast to the rapid growth observed between 2000 and 2020. The analysis identified CO₂ as the primary driver of growth enhancement over the past two decades, but its future influence is expected to decline. Instead, land surface temperature, precipitation patterns, and urban population dynamics are projected to become the dominant factors driving future indirect effects of vegetation growth. These findings offer critical insights into the future acclimation of urban vegetation, supporting improved forecasting and urban planning under global change.