Wetlands conserve biodiversity, store carbon, control erosion, purify water and function as breeding grounds for fish, fowl and invertebrates. In New Zealand, 90 per cent of wetlands have been degraded, drained or destroyed. Many of those are now being restored to their former glory, but new research suggests that they will never function as they once did.

University of California, Berkeley fellow David Moreno-Mateos studied 651 restored wetlands of every type around the world­ from salty estuaries to alpine marshes—50 years to a century after restoration. Despite this long period, they were found to store 23 per cent less carbon than unaltered sites, and had 26 per cent lower plant biodiversity.