Kentleşme, tropiklerin kuş çeşitliliğindeki üstünlüğünü aşındırıyor

For tens of thousands of years, birds and plants have been more varied near the equator than at higher latitudes, a pattern ecologists call the latitudinal diversity gradient. A McGill University study published in PNAS suggests that urban growth is now flattening this gradient. Drawing on eBird, a citizen-science platform built by Cornell University, the team examined more than 10,000 bird species on five continents. They divided the globe into one-square-kilometre cells, kept only those with enough records to capture at least 95% of local diversity, and labelled each one urban, suburban or natural. On average, cities held 32% fewer species than nearby natural land, but the shortfall reached 42% close to the equator and dropped to 12% at 65 degrees of latitude. The authors link this partly to heavier urbanisation in tropical cities and partly to tropical species coping less well with change. Suburbs and greener cities lost less.