New analysis of the habitats of thousands of different plants and animals could be used to find locations for reserves which will conserve the most species at once, scientists said.
A multi-species study identified the most effective areas for conservation in Madagascar, where the government has pledged to triple its network of protected areas to 10% of the island.
And the researchers, writing in the journal Science, say the high-resolution satellite mapping and computer modelling process could be used to identify protected areas in other biodiversity "hotspots" around the world.
Conservation has historically focused on protecting just one species or group, but the team said conserving habitat on that basis in Madagascar could exclude up to half the rare species of other groups.
The study analysed more than 2,300 species from six groups - lemurs, butterflies, frogs, geckos, ants and plants - and mapped their distribution to a one kilometre level.
Before running the computer analysis, species that were rare or had suffered a large amount of habitat loss over the second half of the 20th century were given a higher weighting.
Prioritising just one group for conservation in any given area could neglect almost two-fifths of all species on the unique island, the research found.
The analysis also identified the need to protect habitats which have not previously been targeted for conservation - which has concentrated on large blocks of forest - including areas with low forest cover but lots of endemic species.
There is a trade-off between increasing extinction risks for individual species and providing greater protection for hundreds more, David Lees, butterfly researcher at the National History Museum said. He said it was important to include a wide number of different species and groups in order to protect overall biodiversity rather than just focusing on "cuddly-looking species" or those with particular appeal to humans, such as lemurs.
Around 50% of plant and 71% to 82% of vertebrate species are concentrated in the so-called biodiversity hotspots which cover just 2.3% of the Earth's land area.