Global conservation policies have long used area-based targets to mobilize expansion of protected areas. Despite the uneven distribution of biodiversity, different countries often have used the same global target to guide national plans. Here, we examined the necessity and feasibility of joint action by countries to conserve priorities identified globally for biodiversity and carbon conservation, using 30% (recently set in the Kunming-Montreal Global Biodiversity Framework) and 50% targets, compared with countries conserving their national priorities. Our results show that targeting areas of global significance is much more efficient for biodiversity and carbon conservation, but enormous challenges exist to achieve these targets because of the inequitable conservation challenges between countries and the need to protect landscapes that are utilized by humans for other land uses. We call on countries to take cooperative and coordinated action, supported by strong funding mechanisms, to ensure that the 30% target is equitably and effectively achieved by 2030.