Archive for January, 2015

Planning for the Future – Resilience to Extreme Weather

By Claire Asher, on 15 January 2015

As climate change progresses, extreme weather events are set to increase in frequency, costing billions and causing immeasurable harm to lives and livelihoods. GEE’s Professor Georgina Mace contributed to the recent Royal Society report on “Resilience to Extreme Weather”, which predicts the future impacts of increasing extreme weather events, and evaluates potential strategies for improving our ability to survive, even thrive, despite them.

Extreme weather events, such as floods, droughts and hurricanes, are predicted to increase in frequency and severity as the climate warms, and there is some evidence this is happening already. These extreme events come at a considerable cost both to people’s lives, health and wellbeing, and the economy. Between 1980 and 2004, extreme weather is estimated to have cost around US$1.5 trillion, and costs are rising. A recent report by the Royal Society reviews the future risks of extreme weather and the measures we can take to improve our resilience.

The global insured and uninsured economic losses from the two biggest categories of weather-related extreme events. Royal Society (2014)

The global insured and uninsured economic losses from the two biggest categories of weather-related extreme events. Royal Society (2014)

Disaster risk is a combination of the likelihood of a particular disaster occurring and the impact on people and infrastructure. However, the impact will be influenced not only by the severity of the disaster, but by the vulnerability of the population and its infrastructure, a characteristic we have the potential to change. Thus, while it may be possible to reduce the frequency of disasters by reducing carbon emissions and slowing climate change, another key priority is to improve our own resilience against these events. Rather than just surviving extreme weather, we must adapt and transform.

The risks posed by climate change may be underestimated if exposure and vulnerability to extreme weather are not taken into account. Mapped climate and population projections for the next century show that the number of people exposed to floods, droughts and heatwaves will both increase and become more concentrated.

Exposure risk to floods and droughts in 2090. Royal Society (2014)

Exposure risk to floods and droughts in 2090. Royal Society (2014)

In their recent report, the Royal Society compared different approaches to increasing resilience to coastal flooding, river flooding, heatwaves and droughts. Overall, they found that a portfolio of defence options, including both physical and social techniques and those that utilise both traditional engineering solutions and more ecosystem based approaches. Broadly, approaches can be categorised as engineering, ecosystem-based, or hybrids of the two. Resilience strategies that incorporate natural ecosystems and processes tend to be more affordable and deliver wider societal benefits as well as simply reducing the immediate impact of the disaster.

Ecosystem-based approaches can take a variety of different forms, but often involve maintaining or improving natural ecosystems. For example … Large, intact tropical forests are important in climate regulation, flood and erosion management and … Forests can also act as a physical defence, and help to sustain livelihoods and provide resources for post-disaster recovery. Ecosystem-based approaches often require a lot of land and can take a long time to become established and effective, however in the long-term they tend to be more affordable and offer a wider range of benefits than engineering approaches. For this reason, they are often called ‘no regret’ options. Evidence for the effectiveness of different resilience strategies is highly varied. Engineered approaches are often well-established, with decades of strong research to back them up. In contrast, ecosystem approaches have been developed more recently and there is less evidence available on their effects. The Royal Society report indicates that for coastal flooding and drought, some of the most affordable and effective solutions are ecosystem-based, such as mangrove maintenance as a coastal defence and agroforestry to mitigate the effects of drought and maintain soil quality. In many situations, hybrid solutions may offer the best mixture of affordability and effectiveness.

It is crucial for governments to develop and implement resilience strategies and start building resilience now. This will be most effective if resilience measures are coordinated internationally, resources shared and where possible, cooperative measures implemented. By directing funds towards resilience-building, governments can reduce the need for costly disaster responses later. Governments can reduce the economic and human costs of extreme weather by focussing on minimising the consequences of infrastructure failure, rather than trying to avoid failure entirely. Prioritising essential infrastructure and focussing on minimising the harmful effects of extreme weather are likely to be the most effective approaches in preparing for future increases in extreme weather events.

Original Article:

() Resilience to
extreme weather

Forecasting Extinction

By Claire Asher, on 5 January 2015

Classifying a species as either extinct or extant is important if we are to quantify and monitor current rates of biodiversity loss, but it is rare that a biologist is handy to actually observe an extinction event. Finding the last member of a species is difficult, if not impossible, so extinction classifications are usually estimates based on the last recorded sightings of a species. Estimates always come with some inaccuracy, however, and recent research by GEE academics Dr Ben Collen and Professor Tim Blackburn aimed to investigate how accurate our best estimates of extinction really are.

Using data from experimental populations of the single-celled protist Loxocephalus, as well as wild populations of seven species of mammal, bird and amphibian, the authors tested six alternative estimation techniques to calculation the actual date of extinction. In particular, they were interested in whether the accuracy of these estimates is influenced by the rate of population decline, the search effort put in to find remaining individuals and the total number of sightings of the species. The dataset included very rapid declines (40% a year in the Common Mist frog) and much slower ones (16% per year in the Corncrake), and different sampling regimes.

Their results showed that the speed of decline was a crucial factor affecting the accuracy of extinction estimates – for experimental laboratory populations, estimates were most accurate for rapid population declines, however slow population declines in wild populations tended to produce more accurate results. The sampling regime was also important, with larger inaccuracies occurring when sampling effort decreased over time. This is probably a common situation for many species – close monitoring is common for species of high conservation priority, but interest may decrease as the species becomes closer and closer to extinction. The total number of sightings was also an important factor – a larger number of sightings overall tended to produce more accurate estimates.

Finally, the estimation technique also influenced accuracy, but only in interaction with the other variables mentioned above. Some methods fared best for rapid population declines, others for slower ones. Many of the methods fare poorly when sampling effort changes over time, particularly if it decreases, although they were relatively robust to sporadic, opportunistic sampling regimes. Overall, optimal linear estimation, a statistical method which makes fewer assumptions about the exact pattern of sightings, produced the most accurate results in cases where more than 10 sightings were recorded in total.

This study highlights the challenges faced by ecologists trying to determine whether a species has gone extinct or not. Sightings of rare species are often opportunistic, and only rarely are they part of a systematic, long-term monitoring program. Thus, methods that produce accurate results in the face of changing or sporadic search efforts are of key importance to conservationists. If the history of a species’ population declines and of the sampling effort are known, then statistical estimates can be selected which provide the best estimates for the particular situation. However, this information is rarely available and so using techniques that can provide accurate estimates for a range of different historical scenarios are likely to be of most use in predicting extinction status. Ultimately, it is extremely useful for conservationists to know whether a species is extinct or not, but estimates will always be subject to error except in rare cases (such as the passenger pigeon, for example) where the extinction event is observed first hand. There will always be cases of species turning up years after they were declared extinct, and no estimate will ever be perfect, but understanding the sources of error and the best methods to use to minimise it can be of great benefit in reducing the frequency with which that happens.

Original Article:

() Conservation Biology

This research was made possible by funding from the Natural Environment Research Council (NERC).