Many ecologists seek to restore damaged ecosystems to their original states. But others argue they are being ‘unrealistically nostalgic’ and that invading species open up new ecosystems

WORDS AND their meanings can be every bit as tricky in science as they are in literature. The phrases scientists choose to portray natural phenomena can shape our perceptions of the world, and affect crucial decisions made by policy-makers.

The “novel ecosystems” theory, energetically promoted by a group of influential ecologists in recent years, is a case in point. The theory’s advocates say they are simply describing unprecedented changes in ecosystems, and warning of their consequences.

Their critics claim that the way they have characterised these changes could have a disastrous impact on environmental policy. They say the theory, at least as currently expressed, hands governments and corporations an easy excuse to abandon core conservation targets.

It is no accident that this controversy has arisen in the realm of restoration ecology, a new science that seeks to advance the recovery of ecosystems, where they have been degraded or even destroyed by human activities.

It is a cutting-edge discipline in its active engagement with the enormous complexity of entire ecosystems in the field.

There have been successes in ecological restoration. For example, the Alcoa corporation has been restoring most of the rich biodiversity of a jarrah (eucalyptus) forest in southwestern Australia, after its mining operations have entirely erased not only all the forest vegetation, but also four metres’ depth of soil.

Over the last decade, restoration has become a front-line strategy in global conservation. At home, we have seen expanding restoration of native woodlands and, with more difficulty, of bog ecosystems. Restoration is now written large into European policy, with the EU committed to restoring 15 per cent of degraded landscapes by 2020.

And yet, just at this breakthrough moment, novel-ecosystem theory appears to be undermining, from the inside as it were, basic restoration principles that have only recently been established.

One of the foundational pillars of restoration science is that restoration projects should be based on “historical reference systems”. If you want to restore native oak woodland on a degraded site, for example, you should reconstruct in detail a model of its previously healthy condition. This model becomes the template for the biological communities and ecosystem functions appropriate to your project.

Novel-ecosystem theorists, however, argue that many, perhaps most, of today’s ecosystems are changing so rapidly, and so unpredictably, that attempting to restore to an historical reference system is often a waste of scarce resources.

They say that global human impacts on nature, ranging from climate change to the introduction of invasive alien species, are creating “novel” biological communities. And these new combinations of species may also create unprecedented ecosystem dynamics.

They theorise that such systems have crossed “irreversible thresholds” – radically altered soil composition, for example – that make restoration to historical conditions impossible.

The best we may be able to do, they conclude, is to manage these systems for whatever ecosystem services they can provide. Goodbye oakwoods and bogs, hello rhododendrons and Japanese knotweed as seen at home.

One of the first major papers on the subject, Ecological Restoration and Global Climate Change (2006) stated baldly that: “Valuing the past when the past is not an accurate indicator for the future may fulfil a nostalgic need, but may ultimately be counterproductive in terms of achieving realistic and lasting restoration outcomes.”

What is most surprising, perhaps, is that these views are being propounded by some of the pioneers in the discipline, including Richard J Hobbs, the distinguished and longstanding editor of its most respected journal, Restoration Ecology.

Hobbs and his colleagues are certainly right to sound a warning note. There is, as they put it, a “moral hazard” in promising more from restoration than it can deliver.

They are also right to highlight how rapidly human-induced changes are altering ecosystems, making the always difficult task of restoration to historically-based references increasingly challenging.

It is also true, as they point out, that the currently fashionable conservation compulsion to remove all alien invasive species from restored sites may be not only prohibitively expensive, but also biologically misguided in some cases.

Other senior restorationist scientists and practitioners, however, have not taken kindly to being described as unrealistic nostalgics. They brand the theory as “irresponsible and defeatist”, adding that it offers dangerous pretexts for state and private agencies to “lower the bar” for conservation.

“‘Novel ecosystem’ is a fashionable concept, a cute term,” says Kingsley Dixon, head of science at King’s Park and Botanic Garden in Western Australia. “It has gained currency with people who are saying, ‘Oh, right, I can now define my weed-infested patch as a novel ecosystem.’ It gives legitimacy to the illegitimate.”

When pressed, Hobbs and his colleagues concede that, with sufficient resources, most ecosystems can indeed be restored, which surely casts considerable doubt over their hypothesis of an “irreversible threshold”.

The big threshold for restoration may be economic, and not ecological.

Paddy Woodworth is the author of Restoring the Future, a book on ecological restoration projects worldwide, forthcoming from University of Chicago Press

One person's 'novel ecosystem' is another's 'toxic spill'

The European chapter of the Society for Ecological Restoration (SER) recently held a mini-symposium titled Novel Ecosystems: New Normal or Red Herring?. Some speakers found the concept insightful, but significantly more expressed concern about its policy implications.

"A toxic spill in Spain was described as a 'novel ecosystem' by a mine manager. This is not what Hobbs and his colleagues intended, but the phrase is being used like this." – James Aronson, leading restoration scientist, who organised the symposium

"This phrase gives an alibi to those who do not want to invest in restoration. It is playing with fire. We need scientists to focus on restoration, not on this theory."

– Kris Decleer, researcher and SER Europe board member

"I understand fear of abuse of the term, but I can't understand that, as scientists, we should not be publishing what we observe."

– Jim Harris, co-author of several papers on novel ecosystems with Richard Hobbs

"Global change is happening very fast. There isn't a 'normal' any more. Why do people feel threatened? Is it a case of denial? I understand your concerns, but novel ecosystems may be revolutionary, catalytic and transformational, and we should address that in a creative way."

– Richard Hobbs, lead author on key articles on novel ecosystems