“Build it and they will follow” – said no koala ever

Interesting piece of research to cross my desk today: using koalas to assess whether environmental rehabilitation worked.

It’s part of a larger picture going on in environmental science nowadays about how to make good decisions – which is tricky when you have a complex system you’re working with, limited resources to apply, limited time to act and lots of different opinions about what results are “OK”.

What caught my attention is that this research was basically looking at whether our existing criteria for calling an area “rehabilitated” really work all that well. At the moment, we tend to go out and count the number and selection of plant species thriving, and if that ticks the box we say “good enough”. It’s just been assumed that if you put the plants back, the fauna that used to live in that ecosystem will return and everything will go back to something approximating the old normal. And it’s an easy assumption to make. But, it turns out, it’s not the right assumption.

Researchers at the National Environmental Research Program’s (NERP) Environmental Decisions Hub tried assessing a rehabilitated mine site area by the usual criteria of counting what plants and how many, and then using radio monitoring and poo counts to look in detail at whether koalas did return to the site and if so, to which parts. They found that the koalas paid absolutely no attention to human opinion of the quality of rehabilitation. Whatever it was that koalas thought made a spot work, it wasn’t our nice tidy counts of vegetation or even anything else to do with plants. They were slightly influenced by whether there was a good variety of their favourite foods, but even that didn’t explain their choices. It begs the question “What do koalas want?”.

In this particular piece of research, the scientists followed koalas because that was an animal important to the local community and to the area as a whole – the community were concerned about the decline of koalas in the region. They argue from their results that if there’s a particular animal species or ten that rehabilitators want to see return, just returning the old flora won’t predict success in returning the animals. The best way to decide whether habitat is restored enough to support the animals of interest – and therefore whether you can call a site “successfully rehabilitated” – is going to be to monitor the animals themselves. Which is more work than surveying plants, and more expensive, but the accuracy of the answer is worth it if there are certain animals you really want back in an area.

Original journal article

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