Conservation flipside



David Whitley takes a look at when attempts to save wildlife have unexpected results 

On my last trip to New Zealand, I had an eye-opening visit to the Otago Peninsula. It is home to one of the few remaining colonies of yellow-eyed penguins, the rarest penguin species in the world. Elaborate attempts have been made to protect their nesting sites and get breeding pairs to produce offspring that survive. Yet numbers were still going down.

The problem was that the wildlife sanctuary around the harbour is perhaps too effective. The penguins are protected, but so are the albatrosses and other sea birds. More importantly, the sea lions are protected too – and they prey on the penguins. So while sea lion numbers increase, the penguin numbers go down.

To me, this showed how noble efforts to protect wildlife can often have unforeseen effects. All wildlife is part of an ecosystem, and trying to manage part of that eco-system will always have effects further down the line.

The classic example of this is bufo marinus – better known as the cane toad. It was introduced to Australia from its native South America as a non-chemical means of controlling the cane beetle, which savaged sugar cane crops. The toads didn’t really have much impact on the beetles, but spread across Queensland with no natural predators to keep them in check. Anything that did eat them was poisoned, and native fauna started declining as the competition got too hot.

Other controversial conservation measures in Australia involve the saltwater crocodiles. From the 1930s to 1970s, the big salties were hunted and shot dead in their thousands. By the time hunting them was banned, the population was perilously small – they would have almost certainly died out if the men with shotguns were allowed to keep going.

But since they’ve been protected, numbers have ballooned to the point where some residents in areas where the crocs live are calling for safari-style hunts to be reintroduced. In the Northern Territory in particular, saltwater crocs are encroaching on territory they’ve never previously inhabited, forcing freshwater crocodiles further inland and changing the ecosystems of the creeks and rivers they venture into.

In Queensland, the croc problem is less pronounced, but numbers have undoubtedly grown. And that has led to some interesting theories. One guide I spent a day with reckoned that the increase in saltwater crocodiles had also led to an increase in deadly box jellyfish and irukandji. He reckoned that the crocs eat the sea turtles – which has led to a decline in turtle numbers. Whether that is the reason that the turtles are struggling is open to debate – coastal developments are arguably more likely to reduce turtle numbers as they affect breeding grounds. But it does seem increasingly likely that the turtles were what kept jellyfish numbers down – they’re immune to the toxins, and eat them.

So, fewer turtles means more jellyfish. And the efforts to save the crocs may have something to do with it. When it comes to saving wildlife, nothing is quite as clear cut as it may initially seem.