Should we Move Species Threatened by Climate Change?

by Tracy Rout, University of Melbourne; Doug Armstrong, Massey University; Eve McDonald-Madden, CSIRO; Hugh Possingham; Nicola Mitchell, University of Western Australia, and Tara Martin, CSIRO
 

New Zealand’s ancient tuatara (Flickr/Sheep"R"Us)

Climate change is one of the greatest threats the world’s animals and plants are facing. In fact the world is facing an extinction crisis, which should concern all of us.

The major problem with climate change is not so much that climate is changing, but that it is changing faster than species can move or adapt.

One of the solutions is to move species to places with a more suitable climate.

But the idea of introducing species to areas where they have never occurred before is controversial, because species introduced to somewhere they’ve never lived could have devastating consequences for the species already there. Just think of foxes, lantana, cane toads and other invasive species in Australia.

So how do we weigh up the costs and benefits? In a new study published today in journal PLOS ONE, we developed a way of finding the answer.

Australia’s species at risk

Moving species threatened by climate change isn’t a new idea. In fact we’ve already moved some, while others are being considered.

One of them is the critically endangered Western Swamp Tortoise from Perth in Western Australia - Australia’s rarest reptile. It currently faces extinction thanks to declining seasonal rainfall, which is drying up the swamps the tortoise calls home. To stop the tortoise becoming extinct, scientists have considered potential new sites far to the south of its home range.

Another species facing climate extinction is the Mountain Pygmy-possum, a tiny mammal that currently resides on three snowy mountain tops in Victoria and New South Wales. As temperatures warm the possum is running out of room to move upwards. Snow cover, and the length of time snow stays on the ground, is decreasing rapidly.

This means the possums come out of winter hibernation earlier, and can’t find enough food. The mountains have also seen an influx of feral predators, which previously found the area inaccessible thanks to snow cover.

Weighing up the costs

It’s far from clear cut which species might benefit from this drastic action, and for which it would be a costly and risky mistake. How should wildlife managers approach the decision of whether to move animals into new areas, or leave them in places that may become uninhabitable for them?

In our study we outlined a framework that can quantify whether the benefit of moving a species outweighs the ecological cost.

The benefit of moving a species is based on the likelihood it will go extinct in its original habitat as the local climate becomes hostile, the likelihood that a breeding population can be established at a new site, and the value or importance of the species.

The ecological cost depends on the potential for the species to adversely affect the ecosystem at the new site. Species are considered candidates for re-location only if the benefit of doing so is greater than the ecological cost.

This decision involves both scientific predictions (what’s the likelihood the species will go extinct in its current range?) and subjective judgements (how do we value the conservation of this species compared to species already living at the introduction site?). Our framework separates these questions out.

The framework is intended to support the revised “IUCN guidelines for re-introductions and other conservation translocations”, which explicitly calls for structured decision-making frameworks for conservation introductions.

Testing on tuatara

We test drove our new framework using the hypothetical case of the New Zealand tuatara which is being considered for relocation from its home on a number of small offshore islands in the north of NZ to the South Island, outside of its current range. The tuatara is the country’s largest reptile and the only surviving representative of an ancient lineage.

The tuatara faces a peculiar threat from climate change. Like many reptiles, the sex of a tuatara is determined by incubation temperature, with higher temperatures giving rise to males and lower temperatures to females.

The population from North Brother Island in New Zealand’s Cook Strait is already showing signs of too many males. This is expected to worsen as temperatures increase, putting the population at risk of extinction.

We considered an introduction from the North Brother Island population to a hypothetical mainland sanctuary on New Zealand’s South Island.

We used a previously published population model to predict the effect of climate change on the North Brother Island population, and estimated that the current population of 550 tuatara has a 0.43 chance of persisting in 150 years time. If we remove animals to introduce them elsewhere, this slightly decreases the probability to 0.42.

We found that the chance of successfully establishing a new population was good, and that the chance that the new population will impact negatively on the ecosystem was low.

Tuatara show why it’s essential to have a rigorous framework like this to take the gut instinct and guesswork out of the decision, so we can make smarter choices for conserving species under climate change.

Tracy Rout was lead author on the study. The study was funded by: The ARC Centre of Excellence for Environmental Decisions, The Environmental Decisions Hub of the National Environmental Research Program, The Climate Adaptation Flagship at CSIRO Ecosystem Sciences, The University of Queensland, The University of Melbourne, The University of Western Australia, and Massey University. The same disclosure applies to all other co-authors.

Doug Armstrong received funding as part of the study.

Eve McDonald-Madden received funding as part of the study.

Hugh Possingham received funding as part of the study. He also receives funding from The Australian Research Council, the Department of the Environment (Australian federal government) and a variety of smaller sources. He is affiliated with the University of Queensland (employee), Imperial College London (employee) and World Wide Fund for Nature (Australia - board of governors). He is a member of a variety of community and environmental organisations, and scientific societies.

Nicola Mitchell receives funding from the Australian Research Council and The Western Australian Department of Parks and Wildlife.

Tara Martin received funding as part of the study.


This article was originally published at The Conversation. Read the original article.

Tasmanian Bushfires: Should we Have Trusted the Models?

Tasmanian Bushfires (Photo: James975)

by David Bowman, University of Tasmania

This week the Tasmanian government released its inquiry into the January 2013 bushfires that destroyed numerous properties on the Tasmanian Peninsula.

A key finding is that modelling predicted fires would reach the town 24-hours before it occurred, but this modelling wasn’t disclosed quickly enough.

But putting excessive faith in bushfire modelling is a mistake, particularly as models are not yet sophisticated enough to ensure accurate warnings.

Bushfires across the island had enormous impact on Tasmania: through extensive property damage and harm to the economic, social and psychological well being of affected communities. So a thorough investigation into the causes and consequences of these fires is to be welcomed.

But the bushfire inquiry’s report and the subsequent media reportage has spread a dangerous idea - that government can provide a very high level and reliable community protection from bushfire threats with bushfire models.

Indeed, a powerful storyline in the report is that the Tasmania Fire Service failed to adequately warn communities of the immediate risk of the fires, by not disclosing findings of a predictive model quickly enough.

However, careful reading of the inquiry report undermines this simplistic interpretation about fire models, and glosses over some very serious operational issues concerning the use of bushfire predictions.

The basis for the finding is a match between the actual extent of the Dunalley fire and a 24-hour prediction of the fire spread using an Australian designed bushfire model. But one accurate prediction doesn’t mean we should trust models every bushfire season.

The inquiry acknowledged that fire behaviour is influenced by numerous local factors. These include terrain, fuel loading, fuel type and moisture, and variation in vegetation and winds. Under some conditions severe fires can also create their own weather.

These factors are not perfectly captured in the current generation of predictive fire models, and in any case, the appropriate data are not always available.

The sole expert witness Dr Jon Marsden-Smedley of the University of Tamania to the inquiry - who gave evidence about fire behaviour modelling - stated that the current generation of predictive fire models are imperfect, and are based on generalized meteorological data rather that local measurements.

He also stressed that fire predictions are susceptible to the effects of atmospheric instability that are not represented in the models yet.

Despite the expert advice, the inquiry found that the modelling from January 3, which predicted the town of Dunalley was at risk, should have been acted upon immediately by the Tasmania Fire Service.

The big concern is that such literal application of modelling will lead to “warning fatigue”. Given the limitations of the models there will be numerous false alarms, and there will be some inevitable failures to predict extreme fires. Over time people will become disconnected from fire warnings.

This is a real concern. On the morning of January 4 local communities were clearly warned that a severe fire situation had developed but many people failed to comprehend what these warnings meant, resulting in significant risks to life.

Better is to use the hard won field experience of fire fighters and rural landowners. Local expertise and field experience are critical for assessing fire risk.

Indeed, one of the recommendations of the inquiry is that the Tasmanian Fire Service should place greater reliance on local knowledge from rural landowners. Putting the emphasis on modelling can take this vital knowledge away.

A key organising principle to the inquiry is that the Tasmanian government is duty bound to provide safety and certainty for citizens. The notion that models can provide perfectly reliable advance warning of threat is an appealing idea.

But this can lead to a dangerous thinking with increasing dependence on the state to eliminate fire risk, including an unrealistic expectation of advanced warnings.

Failure to achieve this ideal invites blame, litigation and more fundamentally, people not accepting the responsibilities associated with living in inherently flammable landscapes.

David Bowman receives funding from ARC, NERP, TERN, and NASA.


This article was originally published at The Conversation. Read the original article.