The human jungle

Are pristine rainforests the only ones that matter? We know that forests do change as they age, developing some unique characteristics when mature, and that some species cannot live outside of large swaths of ancient tropical forests.

But what about the rest of tropical forests- the younger ones, the forests that people live in or have cut in recent decades and centuries? Do these have any value? Are there species that can only live in these?

As noted in an article today in the New York Times, around the world, forests are recovering on lands no longer profitable for agriculture, mostly in less productive areas (sloping, poor soils) as people move to urban places and become more connected to urban economies. Moreover, recent evidence shows that most tropical forests may have been farmed or at least burned and cleared at some point in the past 1000 years (for example, in the Americas before Columbus). It may well be that forests untouched by human hand (or fire or plow) may be extremely rare– so rare as to be unimportant to preserving global biodiversity. If this is true, the main difference between one forest and another will just be how long since the last time humans used it.

Perhaps equally importantly, younger forests grab carbon dioxide from the air as they grow- and mature forests have much less capacity to store carbon- the young ones can play a major role in reducing CO₂ in the atmosphere. This does not mean that we should cut old ones and let new ones grow- that will produce the opposite effect in the short term (and the short term matters now!), but it does mean that younger forests should be included in our efforts to control global warming- not ignored as they often are.

At this point in history, the human jungle may well be the jungle that matters the most: used wisely, it can be one key to the future of tropical biodiversity and sustaining a beneficial climate for all of us.

Article in New York Times: http://www.nytimes.com/2009/01/30/science/earth/30forest.html