The illegal killing of elephants in Africa to supply the ivory trade has reached unsustainable rates.

George Wittemyer at Colorado State University in Fort Collins and his colleagues used data from elephant carcass surveys in 45 sites across Africa to model broader trends in elephant poaching on the continent. They found that levels of illegal killing peaked in 2011 at 8% of the global population, leading to the loss of roughly 40,000 elephants, or a 3% overall reduction in animal numbers that year.

Decreasing demand for ivory in China is key to conserving elephants, say the authors.

Proc. Natl Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1403984111 (2014)