The aims of our Research Topic are to provide a global overview of bird population declines, evaluate the main drivers, especially habitat loss and climate change, explore various scenarios for avian biodiversity change, assess the potential ecological consequences of avian biodiversity collapse, and discuss solutions for bird population collapse and biodiversity declines.
The 21st century is the make-or-break century for the world's biodiversity. The global impact of human activities on ecosystems has led to a biodiversity crisis. The current rate of species extinctions may be up to 1,000 times pre-human levels, approaching recognition as Earth's sixth mass extinction event. Loss of species and populations leads to loss of ecosystem services and compromises ecological processes, resulting in direct impacts on human well-being. For terrestrial ecosystems, habitat alteration and climate change are expected to be the greatest drivers of biodiversity loss. Because biodiversity and threats are unevenly distributed around the globe, and funding for biodiversity conservation is limited, identifying drivers of extinction risk and prioritizing funding, research and conservation efforts globally is critical to address biodiversity collapse in the Anthropocene.
Birds are the best-known major group of organisms, comprise excellent environmental indicators, are easily monitored, and, as charismatic flagship species, are met with excitement, enthusiasm, and interest by people worldwide. Therefore, long-term bird conservation and monitoring initiatives that integrate community involvement, capacity-building, outreach, environmental education, and local job creation provide some of the best examples of biodiversity monitoring and conservation programs. As a result, birds are the only group where the conservation status of each species is assessed yearly, making them the best indicators of global biodiversity change. Further, birds are the least threatened major group of organisms, because they are highly mobile, more studied, and there are more conservation resources dedicated to them. Consequently, birds present the best-case scenario for global biodiversity conservation. Factors causing declines and collapses in bird populations are likely to result in even larger declines in other organisms, and, thus, avian population collapses comprise an early warning system for global biodiversity.
Currently, 159 bird species are extinct, nearly a quarter are threatened or near-threatened with extinction, and 44 percent have declining populations. Bird extinctions and population reductions also disrupt important ecosystem processes. Many bird species have irreplaceable roles as dispersers of the majority of the world's tree species, pollinators of thousands of plant species, scavengers of carcasses, nutrient depositors, ecosystem engineers, and predators of vertebrate and invertebrate pests. The societal importance of ecosystem services is often appreciated only upon their loss and losses of birds can change entire ecosystems. Investments in understanding and preventing declines in populations of birds and other organisms will benefit humans and ecosystems, but only while we still have time to act.
For this Research Topic, we especially welcome papers that focus on:
• avian taxa that are particularly susceptible to declines and the reasons for their sensitivity,
• the ecological implications of these declines, including reductions in scavenging, seed dispersal, pollination, predation, nutrient deposition, and ecosystem engineering,
• best practices and successful approaches to avian conservation, including cutting-edge methods and those that emphasize community-based conservation, citizen science, and underserved communities,
• forward-looking analyses and modeling approaches that project the impacts of climate change and habitat loss on avian populations by the end of this century and present realistic scenarios to help prevent species declines and extinctions.
The Topic Editors wish to note that this project is complementary to the Research Topic, "Modern Conservation: Critical Lessons from Birds of Prey". Therefore, relevant spontaneous submissions focusing specifically on raptors should be submitted here.