Forest for the Cars

Curbing an Onslaught of 2 Billion Cars

by William Laurance - bioGraphic

June 2016

Nature could soon be imperiled by twice as many vehicles and enough new roads to encircle the planet more than 600 times.

By 2010, our planet had reached a remarkable milestone: one billion cars—or, to be precise, one billion motorized vehicles, including cars, trucks, buses, and motorcycles but excluding off-road vehicles such as tractors and bulldozers. Of course, the overwhelming majority of these vehicles are powered by fossil fuels. And if that figure isn’t troubling enough, by 2030, it’s projected that we will have double that number: 2 billion cars. Should we reach this ominous milestone, what will it mean for our planet, our environment, and our biodiversity?

Greenhouse Gases 

At the Paris climate conference this past winter, global leaders committed to measures that would limit global warming to 2 degrees C, with a stated aspiration to limit the increase to 1.5 degrees C. As optimistic as I’d like to be about this historic agreement, it’s a bit difficult to see how we’re going to get there in a world with 2 billion smoke-belching vehicles.

In the car-mad U.S., the transportation sector (which is dominated by motorized vehicles but also includes planes, trains, and ships) accounts for 28% of all greenhouse gas emissions, second in significance only to energy generation (34%). As developing nations rapidly expand their use of motorized vehicles, their greenhouse gas profiles will increasingly resemble that of the U.S.

Until recently, diesel engines, which generally burn fuel more efficiently than gasoline engines, have been pushed hard in many nations. However, it’s now understood that, unless operating under optimal conditions, diesels produce large amounts of heat-absorbing soot and toxic nitrogen oxides.

In what has evolved into a spectacular global scandal, German manufacturer Volkswagen even tweaked its software to falsely produce low emissions readings for its diesel cars under test conditions, while belching away on the road.

Highway Holocaust 

There will also be a lot more road-kill on a planet with 2 billion cars. Even now, the numbers are staggering. It has been estimated that roughly 1 million vertebrates (birds, mammals, reptiles, and amphibians) are killed by vehicles in the U.S. each day. In Brazil, the estimate is 1.3 million vertebrates per day. In Europe, as many as 27 million birds are killed along roadways annually. Vehicles also take a massive toll on insects. A study in the Netherlands estimated that 1.6 trillion insects are killed there each year. The total would approach 33 trillion insects, if that same figure were extrapolated to the U.S.

Vehicles can be particularly threatening to species with small populations. According to the Federal Highway Administration, road-kill is a serious threat to 21 endangered or threatened species in the U.S., including Key deer, bighorn sheep, ocelots, red wolves, desert tortoises, American crocodiles, and Florida panthers. Only 100 to 160 Florida panthers survive today, and fully half of all panther deaths are caused by collisions with vehicles. In Australia, vehicles take a heavy toll on echidnas, quolls, wallabies, kangaroos, and the endangered cassowary, among other species. One study estimated that a turtle would have only a 2% chance of surviving a traverse across a busy, multi-lane highway.

Road Pollution 

Vehicles can also be a serious source of chemical and noise pollution. High levels of dust, heavy metals, nutrients, ozone, and organic molecules can extend up to 200 meters from road surfaces. De-icing salts can alter soil and aquatic chemistry and harm roadside vegetation. Effects of chemical pollutants are particularly serious for streams and wetlands near roads, which see major influxes of waterborne pollutants and nutrients entering aquatic ecosystems whenever heavy rains fall. Such contaminants can have wide-ranging impacts, from algae blooms to adverse health effects for aquatic organisms that live in these waterways.

Vehicle noise can also negatively impact wildlife. Many studies have shown that a variety of wildlife species—ranging from grouse to wolves to elk—tend to avoid roads, most likely because of road noise. One study found that migrating birds, which need quality habitats to rest, forage, and rebuild their energy supplies, were disrupted by vehicle noise. Birds near roads spent less time foraging, more time being vigilant, and were in poorer body condition than were individuals that foraged farther away from roads. Low-frequency noises travel much farther away from roads than do higher-pitched sounds and might be particularly disruptive for species that communicate via infrasound, such as elephants and cassowaries. Hence, noisy roads could be invisibly degrading habitats for noise-sensitive wildlife.

Roads as Barriers 

For some species, roads can act as impermeable barriers, effectively fragmenting and reducing their populations. Strictly arboreal species are one obvious example. For instance, my doctoral research showed that movements of lemuroid ringtail possums, which are endemic to the rainforests of northeastern Australia, are completely restricted by roads unless the road clearing is so narrow that branches or vines provide arboreal walkways overhead. Rainforests are rife with such strictly arboreal species.

Even birds can be affected. My wife, Susan Laurance, studied the impacts of roads on specialized rainforest birds in the Amazon. In one insightful experiment, she captured individuals of bird species that are both highly faithful to their territory and to their mate, with whom they pair for life. She could move a bird up to 2 kilometers away in the rainforest and it rapidly returned to its territory and mate, often within the same day. But if she moved the bird across a 250 meter-wide highway clearing, it wouldn’t go home. It moved up and down the forest edge, trying to find a route back, but it never returned.

Roads Everywhere? 

Possibly the worst impact of all those additional vehicles will be the new roads they spawn. It’s currently projected that, by 2050, the world will have another 25 million kilometers of paved roads—enough to encircle the planet more than 600 times.

Today, new roads are being constructed virtually everywhere, including many of the world’s last surviving wild places. We build roads to log forests, to extract fossil fuels and minerals, to increase economic growth and trade, to defend our borders, and to integrate our economies. Around 90% of new roads will be constructed in developing nations, home to the majority of the world’s tropical and subtropical forests—the most biologically rich real estate on the planet.

It would be one thing if we’d just build the roads, but they also open up wild areas to a Pandora’s box of environmental ills—ranging from increased wildlife poaching and forest destruction to wildfires, illegal mining, and land speculation. For example, my research team showed that in the Brazilian Amazon, there are nearly three kilometers of illegal roads for every one kilometer of legal road. Once you map all those roads, you find that 95% of all deforestation in the Brazilian Amazon occurs within 5.5 kilometers of a legal or illegal road.

In many parts of the world, roads are opening up the last surviving stretches of wilderness like a flayed fish. In the Congo Basin, the construction of more than 50,000 kilometers of logging roads has allowed poachers, armed with rifles and cable snares, to conduct a systematic slaughter of wildlife. In the last decade, two-thirds of all forest elephants have been killed. In sub-Saharan Africa, our analyses suggest that a scheme to construct 33 major "development corridors"—spanning some 53,000 kilometers in total—could imperil more than 2,000 parks and protected areas, either by bisecting them or by promoting increased development and poaching around the park.

Globally, the frenetic expansion of roads is probably the single greatest threat to nature. Climate change is eroding ecosystems like an acid, but the proliferation of roads, and the massive environmental perils they bring, are battering away at them like a sledgehammer.

What Are We to Do? 

How can we add another billion cars and not cost the Earth? There are few easy answers, but here are three suggestions.

First, we need to drive smaller, more fuel-efficient vehicles. In Europe, for instance, small and even tiny cars are increasingly becoming the norm. There’s enormous scope for the U.S. and many other industrial and developing nations to move in this direction.

Second, we need to become a lot smarter about where we put roads. Roads should be avoided whenever possible in remaining wilderness areas, sites with high biodiversity and endangered species, and protected ecosystems. In 2014, I led an effort to devise a global roadmap that indicates where roads should and should not go, to maximize their social benefits while limiting their environmental costs.

Finally, we need to raise taxes on petroleum and add surcharges for gas-guzzling vehicles, and use those proceeds to improve public transportation and amenities such as bicycle lanes. There’s simply no sound reason that a single human requires a heavy-duty pickup truck simply to drive around town.

The bottom line is, unless we start thinking hard, and quickly, about ways to curb this vehicular onslaught, we’ll soon be living in an increasingly noisy, polluted, and nature-deprived world where the din of 2 billion cars seems far more like a curse than a blessing.

William Laurance is a distinguished research professor and Australian Laureate at James Cook University in Cairns, Australia. He is the director of the Centre for Tropical Environmental and Sustainability Science, and founder and director of ALERT—the Alliance of Leading Environmental Researchers & Thinkers.