Why cars are bad for koalas
Koalas face a pretty tough time of it. For starters, they only eat highly toxic eucalypt leaves. Such a narrow diet would leave any of us grumpy. No wonder koalas like to sleep for up to 18 hours a day!
In Australia, the distribution of koalas more or less coincides with the highest density of human population. Such close contact with humans has led to a massive decrease in koala numbers. Land clearing, habitat change, predation by dogs and other factors have put massive pressures on koalas.
But one pressure, cars, is having a two-fold effect on koalas. Directly, car traffic and accidents can lead to many koalas perishing on the side of the road. Indirectly, CO2 emissions from cars (and other sources) is fundamentally changing the chemistry of eucalypt leaves making them unpalatable to koalas.
Koala on the road!
Unfortunately, it can be all too easy to run over a koala on the road. Most of the time it is purely accidental. It is very difficult to avoid an animal in the middle of the road as you round a bend at high speed. At night or in the rain it can be even more perilous for koalas.
Road signs, signalling caution, may help. Purpose built overpasses and fences around freeways can direct koalas away from traffic. But others have argued that fences, in particular, merely funnel koalas away from road and towards another. A fence needs to end somewhere, after all.
Motorists can slow down - particularly in areas where koalas are known to be common. Also, as a last resort, a quick response and delivering injured koalas to a nearby koala hospital, such as the Koala Hospital in Port Macquarie, can prevent further loss of life.
Koalas can be surprisingly tough at surviving impacts with cars. A case from South Australia was widely publicized recently of a koala surviving being hit by a car traveling at 100 km/hour. Dubbed 'Bear Grylls', the lucky koala became wedged in the front grill and then survived a further 10km before the driver arrived home and realised the koala was still alive!
CO2 emissions and koalas
Increasing atmospheric carbon dioxide (CO2), not only from cars but from human generated sources generally, is affecting animals in many ways. For example, increasing CO2 is leading to an increase in temperature which, in turn, is making a predator wasp species more sluggish than its prey aphid species leading to the latter to potentially increase in abundance.
Increasing atmospheric CO2 is also altering the chemistry of eucalypt leaves leaving them less palatable to koalas. Like pandas that only eat bamboo, koalas have a very specialised diet of eucalypt leaves from only 7 different types of eucalypt trees. Increasing atmospheric CO2 has been shown to lower the already low nitrogen content of eucalypt leaves and increasing the amount of toxic tannins. Nitrogen is critical for the diet of koalas (and humans) and, therefore, leaves with less nitrogen mean the koala's already unpalatable diet will become even more unpalatable.
Although cars are not entirely to blame for human CO2 emissions, they do nevertheless contribute to the problem.
So what to do about it?
Electric cars may help solve the CO2 emissions problem but they certainly won't prevent further road kill. In fact, the quieter electric cars may lead to even more deaths on roads. Perhaps more signage, greater awareness, fences, overpasses etc will help. Whatever the solution, it will be up to the individual to be just that little bit more alert on the road when they are driving through prime koala habitat.