Even the most conservative estimates predict that 15–40% of living species will be effectively extinct by 2050 as a result of climate change, habitat loss and other consequences of human activities. In the face of such drastic losses, scientists are debating the pros and cons of various, and often controversial, interventions. These include moving populations to help track hospitable habitats, and reinstating keystone species — those that have a large effect on ecosystem structure and function, such as top-level predators — into areas where they have long been absent. Even the revival of species that have recently gone extinct is being explored.

So far, an increasingly viable (and potentially less risky) option, which we call facilitated adaptation, has been little discussed. It would involve rescuing a target population or species by endowing it with adaptive alleles, or gene variants, using genetic engineering.

Over the past 30 years, genetic engineering in agriculture has received substantial attention. Today, 12% of arable land worldwide is planted with genetically modified (GM) crops; the GM seed market alone is valued at US$15 billion. As techniques become ever more sophisticated, more possibilities will open up.