Urban blue-green infrastructure is essential for addressing the challenges posed by urbanization. However, the full extent of its ability to provide ecosystem services, including biodiversity conservation under predominantly anthropogenic climate change, remains unclear. This study evaluates the biodiversity conservation challenges associated with urban blue-green infrastructure under climate extreme scenarios, such as heatwaves, droughts, typhoons, and floods, using highly sensitive and decay-resistant microorganisms, testate amoebae, as indicators of ecosystem health. The studied urban blue-green infrastructure comprises 0.67 km² of forested hills and 3,668 m² of ponds, located within a 55,800 km² city cluster in the Pearl River Delta, South China. The analysis is based on testate amoeba records from 27 soil samples, 30 pond water samples, and pond sediment samples, along with 27 microspatial factors, all collected during consecutive periods of peak warmth or climate extremes in 2021 and 2022. The biodiversity conservation challenges faced by urban blue-green infrastructure in four studied climate extreme scenarios, along with associated water quality concerns resulting from interactions between harmful urban emissions and aquatic ecosystems, are highlighted through the following key findings: Biotope connectivity enabled the redistribution of soil-specific testate amoebae (6 out of 42 species) along hillslopes (moisture gradient) and pond lengths (hydrological gradient). Testate amoebae exhibited strong biotope adaptation, with stochastic processes explaining 69.3% of community variation in water and 78.8% in sediment. Urban blue-green infrastructure became ineffective in mitigating urban emissions, such as CO and NH₃, particularly when testate amoebae were negatively impacted by climate extreme-induced weather conditions and when water quality was further degraded by poor air quality.

Ndayishimiye, J.C., Nyirabuhoro, P., Rui, N., Saldaev, D., Mazei, Y., Gao, X. (2025). Biodiversity conservation challenges in urban blue-green infrastructure under climate extremes: Insights from testate amoeba communities. In: McCarthy, F., Patterson, T., Pendea, F. (Eds.), ISTA-CAP 2025. Program & book of abstracts, Brock University, St. Catharines, Canada.