In a recent interview, the Opposition environment spokesperson Greg Hunt promised to reverse biodiversity decline in five years if the Coalition wins the forthcoming election.

Is this goal achievable? Not the way we’re going. Our investment in enhancing biodiversity is not keeping pace with the factors driving biodiversity declines.

We continue to lose biodiversity by clearing vegetation for mining, urban development and farm management. Queensland’s rate of clearing alone has recently averaged about 100,000 hectares each year, and looks set to increase. Even our national parks have come under attack.

Is it possible to continue to clear land, but also stop biodiversity decline? In theory, perhaps. This is the apparent promise of biodiversity offsetting, an increasingly popular policy approach. But are our current offset policies really designed to halt declines? We argue the answer is no.

No net loss compared to what?

In Australia, the federal government and all state governments have biodiversity offset policies either in place, or in development. Offsetting is done by trading a biodiversity loss in one location with an equivalent gain in another. Biodiversity offset policies usually aim to achieve “no net loss” of biodiversity.

To what extent can biodiversity offsets contribute to halting biodiversity decline? As usual, the devil is in the detail.

Leaving aside the vexed issue of how we actually measure biodiversity, let’s consider what is actually meant by “no net loss” of biodiversity.

The crucial question here is, “no net loss compared to what?” Most people probably imagine that the answer is no net loss of biodiversity compared to what was there before the impact. But this is not usually the case.

Instead, the real intention of most biodiversity offset policies is to achieve no net loss compared to what would have happened in the absence of the impact and the offset. This is often referred to as the counterfactual.

Calculating the compensation

We can see why this definition of “no net loss” emerges if we consider the two ways that offsetting can be done.

First, gains can be achieved through improving existing habitat, or creating habitat from scratch. For example, we could create new wetland habitat for a threatened frog to compensate for a development that destroys its current wetland habitat.

Although there are many limitations to such restoration offsets, they can neutralise damage to some elements of biodiversity.

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Second, we can protect existing habitat as an offset. This is known as an “averted loss” offset, and is the more commonly-used approach.

The assumption here is that protecting against clearing or degradation results in a gain for biodiversity compared to what would have happened without the protection. Calculating this gain requires choosing some sort of “business as usual” rate of decline, based on data on vegetation clearing or degradation of habitat quality.

The gain then occurs because the offset results in better outcomes than would have occurred under the counterfactual “business as usual” scenario. This gain, together with the loss from an impact, provides the “no net loss” outcome.

One of the challenges with this approach is in estimating the counterfactual. It is often (unfortunately) a reasonable assumption that biodiversity will continue to decline. The problem arises when estimating what that rate of decline might be. Since we do very little biodiversity monitoring in Australia, there can be considerable uncertainty around the “business as usual” baseline to which we might compare our offset outcome.

But there are is another important consequence of averted loss offsetting that might not be immediately obvious.

Averted loss offsets only work if biodiversity keeps declining

The crucial point about averted loss offsetting is that it can entrench the baseline rate of decline. That is because the gains from the offset and the losses from the impact are only required to add up to the decline that would otherwise have occurred.

So without additional conservation actions, this approach to offsetting simply ensures current declines continue, at the same rate. This outcome is not a policy failure — it is the way the policy is designed to work.

Allowing this type of averted loss offsetting is therefore an admission that ongoing decline is the norm for our biodiversity. Worryingly, policies structured this way could also provide a perverse incentive to ensure declines continue. This is because without declines, offsets based on “protection” are not possible.

For example, part of the disquiet around increasing protection of vegetation, such as through the Wild Rivers declarations on Cape York, is linked to the potential loss of opportunity to sell offset “credits”. The less of our vegetation we protect, the easier it is to find offsets.

So biodiversity offsets policies that rely heavily on “averted loss” offsetting cannot in themselves reverse declines; they are not designed to. Whether it is fair to expect developers to be responsible not only for negating their impact, but also contributing to improving the lot of biodiversity, is debateable. But we should be aware that offsets are not a panacea. At best, our averted loss offsets will achieve a continuing decline of biodiversity.

At worst, they may provide an incentive for the decline to continue.

What’s new on ice sheet melt?

• 05 Jun 2013, 18:30
• Freya Roberts

Sourced under creative commons

A major review of the latest research on ice sheets is published today in Nature, updating what scientists know about the world’s two biggest bodies of ice – Greenland and Antarctica.

Since the last major climate science report, published by the Intergovernmental Panel on Climate Change (IPCC) in 2007, there have been some big advances in modelling and monitoring ice sheets. That monitoring process is important, because when ice on land melts it drains into the ocean, causing sea levels to rise.

Over the last six years, satellite techniques used to observe changes in ice sheets have improved, allowing scientists to refine estimates of how much ice sheets are contributing to sea level rise. But what do the new and improved modelling techniques tell us about the ice sheets?

Greenland in decline

In Greenland, loss of ice is adding about 0.7 mm to sea levels each year. Surface melting reached record levels in the past few years, but Greenland is also losing chunks of solid ice too. Glaciers and ice flows are transporting more ice from the heart of the ice sheet out to sea where it floats, displacing water and forcing sea levels up.

It’s likely the Greenland ice sheet will drive more sea level rise in the future too, the article says. Although climate models predict more snow will fall over Greenland, those gains are likely to be outpaced by losses from melting and shedding.

The article highlights processes which might amplify ice loss from the ice sheet. For example, both the loss of nearby Arctic sea ice and melting on the surface of the ice sheet reduce the amount of sunlight reflected. Instead, that heat is absorbed, raising surface temperatures.

Antarctica’s mixed picture

At the other end of the planet, the picture is a little less clear. But overall, data indicate the Antarctic ice sheet is losing mass. The review suggests Antarctica is adding a more modest 0.2 mm per year to sea levels.

But different parts of the ice sheet are changing in different ways. The Antarctic Peninsula and West Antarctica is losing solid ice, as huge bodies of ice acting as buttresses to ice flows break up under rising temperatures. But the picture in East Antarctica is somewhat different – here the ice sheet is growing thanks to an increase in snowfall.

As co-author of the paper, Dr Ben Smith from the Polar Science Centre in Washington tells us, there’s still uncertainty about changes in Antarctica, despite the technological advances. One reason is that satellites can only collect data over a small area of the ice, so errors come from scaling up their estimates to cover the entire ice sheet.

Measuring the height of the ice is further complicated by the fact the land beneath the ice is itself changing height, the article notes.

For now at least, the losses outweigh the gains. But scientists aren’t  sure what will happen in the future.

A bigger contribution to sea levels

Despite remaining uncertainties, scientists still have a better idea now of how much ice sheets are raising sea levels compared to a few years ago.

At the time of the last IPCC report (AR4) there was only about 10 years worth of reliable sea level data, from 1993 and 2003. It suggested Greenland and Antarctica were together raising sea levels by about 0.42 mm per year – that’s about 15 per cent of total sea level rise. According to the review, over the next ten years that contribution doubled to about 0.82mm per year:

Smith tells us that increase is down to two things:

“First, we now know better what’s going on in the two ice sheets […] Second, and more importantly, the ice sheets are changing faster than they were in the years leading up to AR4.”

Lead author of the article, Edward Hanna, a Professor at the University of Sheffield adds:

“The main increase [in sea level contribution] has been from the Greenland Ice Sheet due to significant warming, leading to increased melting and discharge of ice over the last 5-10 years whereas Antarctic ice sheet losses seem to be much more modest”

It’s worth bearing in mind these are still quite short time periods, which means natural climate cycles could be affecting what’s driving sea levels. Together with the uncertainties over the data, scientists are still treating these estimates with caution.

But overall, the figures demonstrate what scientists have learned from the last few years of scientific advances – that Antarctica and Greenland are losing mass and driving up sea levels, increasingly fast as time goes on.