Once we establish reserves to protect species or an important biodiversity hot spot, we tend to think those species as ‘safe’. Wrong, says Bill Laurence and a group of over 200 international tropical scientists.
The study of some 60 protected areas in tropical regions found that whilst approximately half are doing well, the other half are declining due to a potent cocktail of invasive species and poor management. However perhaps the biggest problem is what’s going on outside the reserves. The habitat outside a reserve, the matrix, is incredibly important to the health of a reserve. If a reserve is surrounded by intact habitat, then the reserve fared significantly better than those surrounded by urban or cleared agricultural matrices. Isolated reserves will tend to lose species whose small, fragmented populations are cut off from the potentially rescuing effect of gene flow from other individuals. Large animals and predators are also at risk from hunting if they stray beyond the margins of reserves.
So what’s the answer? Establish larger, more connected, reserves. The good news from the study is that over the last two decades, many new protected areas have been established. This has brought the protected area of tropical habitat to 7%, or to 13% if multiple-use reserves are included. However this trajectory needs to continue if we are to continue to conserve species. This research has been covered in a nice article by The Conversation by Bill Laurence.