Habitat fragmentation is having "terrifying" effects on ecosystems

A global surge in habitat fragmentation is simply "terrifying", according to two dozen of the world's top ecologists. 

A forest elephant... not many places to hide anymore.

The authors make this assertion in a paper (which you can download free here) in the leading journal Science Express. 
 
The paper was led by Nick Haddad from North Carolina State University, and includes ALERT members Thomas Lovejoy and Bill Laurance as coauthors.

The study contrasts all of the major experimental studies of habitat fragmentation that have ever been conducted -- including the Biological Dynamics of Forest Fragments Project in central Amazonia, which was founded by Lovejoy in 1979 and is the largest and longest-running of all the experiments.

The study concludes that, almost inevitably, fragmentation has a severe effect on species diversity and ecological functioning -- in ecosystems ranging from rainforests to woodlands to isolated patches of moss.

One of the key drivers of change in ecosystems is edge effects -- physical and biological changes associated with the abrupt, artificial edges of habitat fragments.  For instance, you often see more tree mortality, fires, microclimatic stresses, and invasive species near edges.

The study concluded that 70 percent of all the world’s forests are now within one kilometer of a forest edge, and 20 percent is within a football field of an edge.
 
“There’s really only two big blocks of forest surviving on Earth today,” said Professor Haddad.  “That’s the Amazon and Africa’s Congo Basin.”
 
And even those great forests are under assault.  For example, loggers have bulldozed more than 50,000 kilometers of new roads into the Congo since the year 2000.  As a result, the forests have been invaded by poachers with modern weapons, who have killed off two-thirds of the world’s forest elephants for their valuable ivory tusks.
 
The study was highlighted in an excellent article in the famous New Yorker magazine.  It underscores that fact that roads really are the biggest danger.

Once a road cuts into a forest, we often see an influx of illegal colonists, loggers, poachers and miners, especially in developing nations where the rule of law is often limited.
 
In the Amazon, for instance, 95 percent of all deforestation occurs within five kilometers of a road. 

The take-home message is obvious: If we’re going to preserve parts of wild nature for future generations, we simply must keep the roads out.