Are degraded tropical forests worth saving?

Humans are increasingly dominating the tropical world.  For conservationists and researchers alike, a key question is this: To what degree will human-degraded habitats be able to sustain tropical biodiversity?

Conserving specialists is the trickiest part

Conserving specialists is the trickiest part

A new study by Ricardo Solar and colleagues, just published in the leading journal Ecology Letters, has some compelling answers for us.

The study involved ambitious field research on a range of organisms -- plants, birds, bees, ants, and dung beetles -- in the Brazilian Amazon.

The researchers found that intensive land-uses, such as cattle pastures and soy farming, basically blitz biodiversity. 

Only a small fraction of all species can survive in these heavily exploited areas, and they tend to be similar kinds of species -- disturbance-loving generalists that are good at living in highly degraded habitats.

Not much biodiversity here

Not much biodiversity here

The same pattern happens again and again, regardless of which group of organisms one is studying.  This consistency gives one a lot of confidence in the authors’ conclusions.  Intensive land uses such as crop production and ranching are generally really bad for biodiversity.

However, the authors also show that, for disturbed or regenerating forests, the pattern is more complicated.  In these areas, you can get richer and quite different sets of species living in different places. 

This means that these altered forests still harbor quite a lot of biodiversity, especially when one looks across the entire landscape and adds up all the different species living in the various kinds of altered forests. 

It’s not as much biodiversity as you’d find in undisturbed, old-growth rainforests, but there’s still a lot of biodiversity there.

Hence, any kind of forest has value for biodiversity -- even if it is quite heavily damaged. 

Old-growth rainforests are definitely the best, especially for conserving really specialized species.  But we definitely shouldn’t ignore the importance of forest regrowth, habitat fragments, and logged forests either. 

Moreover, above and beyond providing a home for biodiversity, disturbed or regenerating forests can play important roles in carbon storage, hydrological functioning, soil conservation, and water purification.

The bottom line: All forests are good.  The less disturbed they are, the better.  But we shouldn't ignore the value of any kind of forest for aiding tropical biodiversity and ecosystem health.