As we celebrate the International Day for Biological Diversity on 22 May, Singapore — a participant in the preparatory committee of the 1992 United Nations Earth Summit and a signatory to the Convention on Biological Diversity — is making another contribution.

In addition to its proposed index on cities' biodiversity, to measure urban efforts towards conservation and sustainable development (Nature 460, 33; doi:10.1038/460033a 2009), Singapore is to construct an ecological corridor known as the Eco-Link over the Bukit Timah expressway. With completion expected by 2013, this hourglass-shaped bridge will re-establish a connection that was severed in 1985 between the city's Bukit Timah and Central Catchment nature reserves.

The corridor is intended for tropical conservation and should redress trade-offs made in the past for economic reasons. It has been compared with Natuurbrug Zanderij Crailo ('Crailo sand-quarry nature bridge') in the Netherlands. However, its tropical setting is likely to pose engineering and restoration difficulties, owing to the diversity of tropical habitats and inhabitants.

It will be planted up like a forest to enable animal and plant transfer between the two reserves. Longer term, it is hoped that the corridor will restore the ecological balance in the fragmented habitats and rectify the loss of biodiversity. If successful, it could be replicated in other tropical cities to help conserve native biodiversity and to teach us how to restore degraded natural landscapes.

It is instructive that a nation as small, land-scarce, resource-poor and highly urbanized as Singapore is leading this promising initiative.