Habitat fragmentation may be causing birds to lose genetic diversity far faster than previously estimated. A study of 62 songbird species in China found that all had lost nearly half their genetic diversity over roughly 50 years, including species considered common and at low risk of extinction. Human activity has dramatically altered natural landscapes, accelerating biodiversity loss and threatening species not only through declining populations but also through the erosion of genetic diversity, which is essential for long-term survival and adaptation. However, studies have produced conflicting estimates of how quickly genetic diversity is disappearing, leaving uncertainty about the true effects of habitat destruction and fragmentation. To address this gap, Ri Liu and colleagues investigated changes in genetic diversity across 62 songbird species in China's Gaoligong Mountains, a biodiversity hotspot where forest fragmentation has intensified sharply in recent decades. By comparing genomic samples collected from the 1960s and 1970s with those gathered between the 2000s and 2020s, Liu et al. tracked genetic changes over roughly five decades and evaluated how habitat fragmentation, species abundance, and dispersal ability influenced genetic decline.
The authors found that all 62 species lost an average of 43% to 49% of their genetic diversity over roughly the last 50 years – a decline far greater than many previous estimates. The findings suggest that habitat fragmentation is a primary driver of this genomic erosion, particularly among species with limited dispersal abilities. Surprisingly, even species considered common and widespread also experienced substantial genetic losses, despite their relatively large populations. Liu et al. note that because all 62 songbirds in the study are classified as "Least Concern" on the Red List of Threatened Species, the findings reveal a hidden conservation risk – species that appear secure by conventional measures may be losing the genetic variation needed to adapt to environmental change and persist over time. They argue that genomic monitoring should become a more integral part of conservation efforts to detect these declines before they translate into more visible population losses.
