The study by Jetz, Wilcove, and Dobson assesses the projected impacts of climate change and land-use change on the global diversity of birds. Using the Millennium Ecosystem Assessment (MA) scenarios, the authors evaluate the exposure of 8,750 land bird species to future land-cover changes. The analysis assumes stationary geographic ranges, which may overestimate actual losses but provides a baseline for comparison. Under all scenarios, even those that are environmentally benign, at least 400 species are expected to experience >50% range reductions by 2050, and over 900 by 2100. While climate change will significantly affect biodiversity, land-use change in tropical regions is projected to cause even greater species loss. The authors emphasize the need for an expanded reserve network in the tropics and more ambitious goals to reduce greenhouse gas emissions to minimize global extinctions. The study highlights the critical role of socioeconomic pathways in determining the magnitude and geographic patterns of potential range loss, with reactive management leading to greater losses due to direct human land transformation.The study by Jetz, Wilcove, and Dobson assesses the projected impacts of climate change and land-use change on the global diversity of birds. Using the Millennium Ecosystem Assessment (MA) scenarios, the authors evaluate the exposure of 8,750 land bird species to future land-cover changes. The analysis assumes stationary geographic ranges, which may overestimate actual losses but provides a baseline for comparison. Under all scenarios, even those that are environmentally benign, at least 400 species are expected to experience >50% range reductions by 2050, and over 900 by 2100. While climate change will significantly affect biodiversity, land-use change in tropical regions is projected to cause even greater species loss. The authors emphasize the need for an expanded reserve network in the tropics and more ambitious goals to reduce greenhouse gas emissions to minimize global extinctions. The study highlights the critical role of socioeconomic pathways in determining the magnitude and geographic patterns of potential range loss, with reactive management leading to greater losses due to direct human land transformation.