A refocus on managing military training grounds for their value to the environment as well as to the armed forces would drastically increase the global terrestrial 'protected area' at minimal cost (see J. E. M. Watson et al. Nature 515, 67–73; 2014).

We estimate that training areas total at least 50 million hectares, with the actual figure probably closer to 300 million hectares (R. Zentelis and D. Lindenmayer Conserv. Lett., in the press). These areas encompass all major global ecosystems, including those poorly represented within formal reserve systems. In the Western world, at least, their management is already funded through military expenditure.

Many examples highlight the value of such areas. They support the majority of Germany's wolf packs, and in Australia they contain some of the best remaining threatened coastal heathland. Regardless of one's view of the military, the armed forces manage a huge area of land that, until now, has not been recognized as an important funded conservation resource.