For wildlife, huge difference between different kinds of agriculture

We live in an increasingly human-dominated world, where once-intact native habitats are being rapidly fragmented into smaller 'islands' surrounded by a hostile 'sea' of human land-uses.  But for wildlife, not all human land-uses are equal.

Bobcats like having trees overhead

Bobcats like having trees overhead

A recent study in southern California shows that the bobcat, an important but shy wildlife species, is affected very differently by different types of farming.

Like most species, bobcats must move to survive.  Animals trapped in small habitat fragments live in populations too small to be viable.  Bobcats are therefore far more likely to survive if human-dominated lands surrounding habitat fragments are 'permeable' to their movements.

One way to make fragmented landscapes more permeable is to create movement corridors linking the fragments together -- what some have called "bandages for wounded landscapes". 

Another way is to use less-hostile types of agriculture that pose less of a barrier to sensitive species.  For bobcats, it turns out that orchards pose considerably less of a barrier to movements than do intensively cultivated row-crops such as maize, soy, and sugar beets.

Bobcats used row crops only rarely, and even then tried to dash through them quickly, evidently feeling highly vulnerable.  However, their movements in orchards were much more relaxed and similar to those in native habitats.

Studies in the tropics have similarly shown that agriculture that retains tree cover is often much more benign for nature. 

In the New World tropics, for instance, birds, bats, and many other species tend to be much more abundant in shade-cacao plantations (used for producing cocoa), where larger trees are retained or grown to shade the cacao trees, than in more intensively used lands. 

Bare-eyed antbird, an understory specialist in New World rainforests

Bare-eyed antbird, an understory specialist in New World rainforests

Wildlife diversity is especially high when native tree species are retained in the shade-cacao plantations, rather than using exotic fruit or timber species.  Another big bonus for wildlife is having native forest nearby the shade-cacao plantation.

However, shade-cacao is not a panacea for tropical species.  The most sensitive wildlife, such as understory birds, rarely use cacao and are mostly restricted to native rainforest.

The bottom line: native habitats are always the best, but when agriculture is unavoidable, not all types of farming are created equal.  Understanding how different farming methods affect wildlife -- and which wildlife species are most vulnerable -- will give us a leg up for managing and conserving nature.


Rate of tropical rainforest destruction leaps by 62 percent

Globally, tropical rainforests are getting hammered even faster than we thought.  This is grim news indeed for the planet's biologically richest real estate.

Pardon me, thou bleeding piece of Earth... forest loss in Cambodia  (photo by William Laurance)

Pardon me, thou bleeding piece of Earth... forest loss in Cambodia (photo by William Laurance)

That's the conclusion of an important new analysis that used detailed Landsat data to assess deforestation rates from 1990 to 2010, in tropical nations that contain about 80% of the world's remaining rainforests.

The study, led by Do-Hyung Kim of the University of Maryland, USA, contrasted average rates of tropical deforestation between 1990 and 2000, and between 2000 and 2010. 

The authors found that the net rate of forest loss (the deforestation rate minus the rate of forest regeneration and afforestation) jumped from 4 million hectares per year in the 1990s to 6.5 million hectares per year in the 2000s -- a 62 percent increase overall.

In the 2000s, Brazil was the fastest forest-destroying nation worldwide, according to the authors.  However, its deforestation rate in Amazonia began falling in the mid-2000s and is now just 25% or so of its former rate.

Southeast Asia is the major tropical region in the worst shape, with less forest than either the New World or African tropics and the highest relative rate of forest loss.

Deforestation rates are relatively modest in Africa but are accelerating in the Democratic Republic of Congo and Madagascar -- both vital hotspots for biodiversity.

Notably, the University of Maryland study differs in its conclusions from a major analysis by the FAO (United Nations Food & Agricultural Organization). 

The FAO study concluded that deforestation had fallen in the 2000s, relative to the 1990s, but the University of Maryland researchers say the FAO missed important centers of deforestation that were obvious in their satellite analyses.

Clearly, it's time to redouble our conservation efforts in the tropics -- or we may be remembered as the generation that stood by and watched the rainforests die.