The length of roads in Congo Basin logging concessions has doubled since 2003, according to new research, raising concerns about the impacts of these incursions into the world's second-largest bank of tropical forest.
The authors of the study, published June 24th in the journal Nature Sustainability, note that roads allow people to enter new frontiers, often leading to a contagion of deforestation for agriculture and increased hunting of the animals found there.
"That obviously bodes alarmingly for everything from forest elephants to gorillas and chimpanzees and lots of other wildlife that are subject to hunting," William Laurance, a tropical ecologist and professor at James Cook University in Cairns, Australia, said in an interview.
Deforestation rates around the oldest roads in the Congo Basin are about four times what they were at the beginning of the 21st century, and numbers of key species have dropped off considerably. There are only about a third as many forest elephants alive today compared to 10 years ago, for example.
Following a journey across several Congo Basin countries several years ago, Laurance and Fritz Kleinschroth, the paper's lead author, decided to use existing satellite data to understand how the region's road network has evolved since 2003. The team also calculated the deforestation in the immediate area around logging roads, and they compared the persistence of roads inside and outside designated logging concessions.
They found that the length of roads increased by 54,000 miles to 143,500 miles in the Congo Basin between 2003 and 2018. The rate of expansion outside concessions was somewhat less than inside, at around 40 percent. But the rate of forest loss was higher along roads beyond concession boundaries.
The analysis also showed that roads inside these logging areas are about four times as likely to be abandoned. Shuttering access to roads not only allows forest to regenerate along the road's path, but it also potentially reduces the deforestation that often follows the human settlement of an area.
The logging companies with licenses to harvest trees abandoned 44 percent of logging roads over the period examined in the study. In contrast, only 12 percent of roads were abandoned beyond the borders of these concessions.
"It can make a big difference," Laurance said. "That's where [selectively logged] timber concessions start to look like a more sustainable alternative rather than facilitating deforestation, which clearly they do in some cases."
In the Democratic Republic of Congo, where fewer logging concessions exist due to a sporadically enforced moratorium on new licenses in place since 2002, deforestation typically occurs at higher rates around roads than in neighboring countries. Previous research shows that up to about 90 percent of logging takes place informally, and often illegally, in DRC.
Roads also facilitate the establishment of small-scale agriculture, which studies in recent years have shown is the most significant driver of deforestation in the country. The authors also note that even more deforestation could occur at the hands of loggers as DRC's leaders issued concession permits covering 2,500 square miles to Chinese companies in 2018.
Shutting roads off to further use once companies have cut the allowed amount of timber in a given area could minimize the hunting, mining, and deforestation that occurs in the wake of road construction, Laurance said, particularly with measures that have proved effective, such as the destruction of bridges. But, he added, it should happen more often.
"It's not like 80 percent of the roads are being closed," Laurance said.
Kleinschroth, a tropical ecologist at ETH Zurich, agreed.
"Companies could do more in actively closing and actively making sure who is using which roads," he said.
Still, Kleinschroth said he understands the desire to build out road networks in these countries, which are among the poorest in the world. Roads are often seen as a first step toward economic development. Though future road maintenance costs, particularly in the rain-soaked tropics, are often woefully underestimated, officials sometimes strike deals with logging companies to keep roads open or even pave them as a way of encouraging commerce within the country and throughout the Congo Basin.
"In this region, there are some countries that do not have permanent road connections with neighboring countries," Kleinschroth said. "That's extremely rare that two neighboring countries are not even reachable by road, so I understand their reasoning from a perspective of economic development.
"We shouldn't be too quick to criticize building a road," he added.
This story originally appeared at the website of global conservation news service Mongabay.com. Get updates on their stories delivered to your inbox, or follow @Mongabay on Facebook, Instagram, or Twitter.