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Bioperversity in the Plantation

By David Salt

A narrow focus on carbon in commercial plantations could yield a number of unwelcome surprises.

Like it or not, the carbon economy is coming to town. No one can predict exactly what it will look like, but the bottom line is that emitting or capturing carbon is going to have a price.

One of the expected consequences of this is that income from carbon offsetting will drive major land management changes. Land owners will be shifting land to higher carbon storage states by transforming the vegetation cover. Many people say this is a good thing, with the potential to restore degraded land and better protect biodiversity.

But a growing number of scientists are also advising caution – that a narrow focus on carbon storage has the potential to create significant negative environmental outcomes if the protection and enhancement of other values such as biodiversity are not explicitly considered. Researchers at the ARC Centre of Excellence for Environmental Decisions (CEED) have even come up with a name for it: “bioperversity”.

When it comes to locking up carbon, one popular strategy frequently put forward is the establishment of massive commercial-scale tree plantations transforming whole landscapes. Such ventures, it is proposed, lock up carbon while at the same time growing a valued commodity. The claim of other associated environmental benefits is also often thrown in.

“Incentives to sequester carbon through establishing plantations are likely to increase as the impacts of climate change become more pronounced and intense,” says Prof David Lindenmayer, the lead researcher on a recent review of plantations for carbon sequestration and biodiversity. “We argue that harmful outcomes for biodiversity – what we term ‘bio-perversities’ – can arise as unintended consequences from a range of efforts to enhance forest-based carbon sequestration. Perhaps the greatest of the associated potential bio-perversities are those which may arise from ill-conceived or inappropriate large-scale plantation projects.”

Broadly speaking, there are three areas of bio-perverse outcomes arising from carbon sequestration plantations:

1. land clearing to establish tree plantations,

2. the risks of plantation trees becoming invasive plants; and

3. the potential for plantations to negatively affect key ecological processes and disturbance regimes.

These threats reflect some of the well-documented causes of global biodiversity loss; these being habitat loss, invasive species, and threats from human-altered ecosystem processes. What’s more, each of these negative impacts associated with plantations have occurred in many places in the past, and that was before the emergence of the issue of climate change. So, if these threats are not explicitly dealt with when rolling out new policies on carbon plantations, there’s a very real expectation they will occur again, but on a far greater scale.

“But we believe this doesn’t have to be so,” says Lindenmayer. “And we’ve proposed four strategies to mitigate the risk. These involve ecological risk assessments, full carbon accounting of ecosystems and proposed management activities, an examination of incentives used to stimulate the establishment of tree plantations, and the establishment of compliance and ecological monitoring programs to detect bio-perverse outcomes.

“Each of these four strategies would deal with the three areas of bio-perversity to differing degrees. As just one example, in considering the risk of land clearing to establish tree plantations, full carbon accounting assessment of areas being considered for conversion to plantations will be of particular importance. Such an accounting may demonstrate the carbon sequestration value of maintaining native forest or grassland compared with the establishment of a plantation. As an example, several studies have shown that monocultures of plantation trees may take longer to produce a net carbon gain and ultimately store less carbon in above ground biomass and soil organic carbon than native primary forests, secondary (regenerating) native forests, and multistrata agro-forestry plantings.

“If the rush to plant trees and establish plantations for carbon sequestration results in a range of other environmental values being ignored, we expect big problems to follow. A narrow focus on carbon may well exacerbate a range of existing environmental problems, contribute to further biodiversity loss, introduce additional obstacles to recovering or maintaining the ecological integrity of environments, and ultimately fail to mitigate the anthropogenic causes of climate change. And that would be a perverse outcome indeed of a venture that was intended to ameliorate the root cause of climate change.”

David Salt is a science writer at the Australian National University and is part of the ARC Centre of Excellence for Environmental Decisions.