Biodiversity holds the foundation of ecosystem processes. It supports pollination, nutrient cycling, carbon sequestration, climate regulation, and the structural integrity of food webs. In urban contexts, biodiversity performs additional functions that directly affect human welfare: trees and vegetation reduce ambient temperatures, attenuate stormwater runoff, improve air quality, and provide psychosocial benefits to residents. Rich bird diversity, in particular, has been repeatedly associated with positive physical and mental health outcomes for urban populations. The loss of biodiversity, therefore, is not merely an ecological concern but a threat to human wellbeing and urban resilience.

Despite its significant importance, biodiversity is under unprecedented global threat, driven primarily by land-use change and urban expansion. Urbanization is now the most pervasive and fastest-growing form of land transformation worldwide, converting diverse natural ecosystems into impervious surfaces, fragmenting habitats and replacing ecologically complex communities with a homogeneous assemblage of disturbance-tolerant species [6, 7]. By 2050, urban populations are projected to grow by 2.5 billion people, with roughly 90% of this growth concentrated in Asian and African regions, where it extensively overlaps with global biodiversity hotspots [8, 9]. Urban development thus puts direct pressure on the very landscapes that harbor the highest biological richness on Earth.

As natural cover is replaced by built environments, habitat is reduced to small, isolated fragments surrounded by an inhospitable urban matrix of roads, buildings, and impervious surfaces. This fragmentation severs ecological connections, interrupts species movement, reduces gene flow, and ultimately erodes local biodiversity through the extinction of habitat specialists and the proliferation of generalist and non-native species. For island nations with endemic-rich biota and limited land area such as the Philippines, these dynamics are especially significant, because species have no continental refuge as urban pressures intensify.