Mammal diversity will take millions of years to recover from the current biodiversity crisis

Abstract

<p id="d5647668e202">Biodiversity is more than the number of species on Earth. It is also the amount of unique evolutionary history in the tree of life. We find that losses of this phylogenetic diversity (PD) are disproportionally large in mammals compared with the number of species that have recently gone extinct. This lost PD can only be restored with time as lineages evolve and create new evolutionary history. Without coordinated conservation, it will likely take millions of years for mammals to naturally recover from the biodiversity losses they are predicted to endure over the next 50 y. However, by prioritizing PD in conservation, we could potentially save billions of years of unique evolutionary history and the important ecological functions they may represent. </p><p class="first" id="d5647668e205">The incipient sixth mass extinction that started in the Late Pleistocene has already erased over 300 mammal species and, with them, more than 2.5 billion y of unique evolutionary history. At the global scale, this lost phylogenetic diversity (PD) can only be restored with time as lineages evolve and create new evolutionary history. Given the increasing rate of extinctions however, can mammals evolve fast enough to recover their lost PD on a human time scale? We use a birth–death tree framework to show that even if extinction rates slow to preanthropogenic background levels, recovery of lost PD will likely take millions of years. These findings emphasize the severity of the potential sixth mass extinction and the need to avoid the loss of unique evolutionary history now. </p>