Massive yet grossly underestimated global costs of invasive insects

4 10 2016
Portrait of a red imported fire ant, Solenopsis invicta. This species arrived to the southeastern United States from South America in the 1930s. Specimen from Brackenridge Field Laboratory, Austin, Texas, USA. Public domain image by Alex Wild, produced by the University of Texas "Insects Unlocked" program.

Portrait of a red imported fire ant Solenopsis invicta. This species arrived to the southeastern USA from South America in the 1930s. Specimen from Brackenridge Field Laboratory, Austin, Texas, USA. Public domain image by Alex Wild, produced by the University of Texas “Insects Unlocked” program.

As many of you already know, I spent a good deal of time in France last year basking in the hospitality of Franck Courchamp and his vibrant Systematic Ecology & Evolution lab at Université Paris-Sud. Of course, I had a wonderful time and was sad to leave in the end, but now I have some hard evidence that I wasn’t just eating cheese and visiting castles. I was actually doing some pretty cool science too.

Financed by BNP-Paribas and Agence Nationale de Recherche, the project InvaCost was designed to look at the global impact of invasive insects, including projections of range dynamics under climate change and shifting trade patterns. The first of hopefully many papers is now out.

Just published in Nature Communications, I am proud that many months of hard work by a brilliant team of ecologists, epidemiologists and economists has culminated in this article entitled Massive yet grossly underestimated costs of invasive insects, which in my opinion is  the first robust analysis of its kind. Despite some previous attempts at estimating the global costs of invasive species1-4 (which have been largely exposed as guesswork and fantasy5-10), our paper rigorously treats the economic cost estimates and categorises them into ‘reproducible’ and ‘irreproducible’ categories.


Gypsy moth (Lymantria dispar) adult. Dimitri Geystor (France)

What we found was sobering. If we look at just ‘goods and services’ affected by invasive insects, the annual global costs run at about US$70 billion. These include agricultural, forestry and infrastructure damages, as well as many of the direct costs of clean-up and eradication, and the indirect costs of prevention. When you examine that number a little more closely and only include the ‘reproducible’ studies, the total annual costs dip to about US$25 billion, meaning that almost 65% of the costs recorded are without any real empirical support. Scary, especially considering how much credence people put on previously published global ‘estimates’ (for example, see some citation statistics here).


Formosan subterranean termite Coptotermes formosanus by Scott Bauer, US Department of Agriculture, Agricultural Research Service

There’s a great example to illustrate this. If you take it at face value, the most expensive invasive insect in the world is the Formosan subterranean termite Coptotermes formosanus estimated at US$30.2 billion/yr globally. However, that irreproducible estimate is based on a single non-sourced value of US$2.2 billion per year for the USA, a personal communication supporting a ratio of 1:4 of control:repair costs in a single US city (New Orleans), and an unvalidated assumption that the US costs represent 50% of the global total.

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Transition from the Anthropocene to the Minicene

24 09 2016
Going, going ...

Going, going … © CJA Bradshaw

I’ve just returned from a life-changing trip to South Africa, not just because it was my first time to the continent, but also because it has redefined my perspective on the megafauna extinctions of the late Quaternary. I was there primarily to attend the University of Pretoria’s Mammal Research Institute 50thAnniversary Celebration conference.

As I reported in my last post, the poaching rates in one of the larger, best-funded national parks in southern Africa (the Kruger) are inconceivably high, such that for at least the two species of rhino there (black and white), their future persistence probability is dwindling with each passing week. African elephants are probably not far behind.

As one who has studied the megafauna extinctions in the Holarctic, Australia and South America over the last 50,000 years, the trip to Kruger was like stepping back into the Pleistocene. I’ve always dreamed of walking up to a grazing herd of mammoths, woolly rhinos or Diprotodon, but of course, that’s impossible. What is entirely possible though is driving up to a herd of 6-tonne elephants and watching them behave naturally. In the Kruger anyway, you become almost blasé about seeing yet another group of these impressive beasts as you try to get that rare glimpse of a leopard, wild dogs or sable antelope (missed the two former, but saw the latter). Read the rest of this entry »

More things stay the same, more we retrogress

20 07 2016

obrazek_1idiommmmsmmWithin six months of Abbott and the Coalition seizing power in the 2013 Australian election, decades—if not centuries—of environmental damage and retrograde policies unfolded. But this was no run-of-the-mill incompetence and neglect by government—this was an all-out attack on anything with the merest whiff of environmental protection. The travesty is well-documented, from infamously axing both the carbon-pricing scheme and climate commission, eradicating Labor’s 80% emissions-reduction target by 2050, diluting the Renewable Energy Target, refusing to commit to enforcing the Illegal Logging Prohibition Act (fortunately, this is now law), defunding the only independent legal entity available to limit environmentally destructive development (Environmental Defenders Office), to even attempting to remove the rights of environmental groups to challenge development proposals (thankfully, that failed).

The Coalition’s backward and ineffectual climate change-mitigation policies alone are evidence enough for long-term damage, but their war on the environment in general means that even the future election of a more environmentally responsible government will not undo the damage quickly, if at all. As a result of these and other nearsighted policies, Australia remains one of the highest per-capita greenhouse-gas emitters on the planet, has one of the highest per-capita water uses of any nation, leads the world in mammal extinctions, continues to deforest its already forest-poor landscape, and is a society utterly unprepared to deal with the future challenges of a degraded planet.
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Seeing the wood for the trees

11 07 2016
The Forest Synopsis: Photo of the Anamalai Tiger Reserve, India, by Claire Wordley

The Forest Synopsis: Photo of the Anamalai Tiger Reserve, India, by Claire Wordley

From the towering kapoks of South America to the sprawling banyans of South Asia, from misty cloud forests to ice-covered pines, forests are some of the most diverse and important ecosystems on Earth. However, as conservationists and foresters try to manage, conserve and restore forests across the world, they often rely on scanty and scattered information to inform their decisions, or indeed, no information at all. This could all change.

This week sees the launch of the Forest Synopsis from Conservation Evidence, a free resource collating global scientific evidence on a wide range of conservation-related actions. These aim to include all interventions that conservationists and foresters are likely to use, such as changing fire regimes, legally protecting forests or encouraging seed-dispersing birds into degraded forests.

Making conservation work

“We hear a lot about how important it is to do evidence-based conservation”, says Professor Bill Sutherland at the University of Cambridge, UK, “but in reality getting a handle on what works is not easy. That’s why we set up Conservation Evidence, to break down the barriers between conservationists and the scientific evidence that they need to do their jobs.” Read the rest of this entry »

Shadow of ignorance veiling society despite more science communication

19 04 2016

imagesI’ve been thinking about this post for a while, but it wasn’t until having some long, deep chats today with staff and students at Simon Fraser University‘s Department of Biological Sciences (with a particular hat-tip to the lovely Nick Dulvy, Isabelle Côté & John Reynolds) that the full idea began to take shape in my brain. It seems my presentation was a two-way street: I think I taught a few people some things, and they taught me something back. Nice.

There’s no question at all that science communication has never before been so widespread and of such high quality. More and more scientists and science students are now blogging, tweeting and generally engaging the world about their science findings. There is also an increasing number of professional science communication associations out there, and a growing population of professional science communicators. It is possibly the best time in history to be involved in the generation and/or communication of scientific results.

Why then is the public appreciation, acceptance and understanding of science declining? It really doesn’t make much sense if you merely consider that there has never been more good science ‘out there’ in the media — both social and traditional. For the source literature itself, there has never before been as many scientific journals, articles and even scientists writing. Read the rest of this entry »

Sensitive numbers

22 03 2016

A sensitive parameter

You couldn’t really do ecology if you didn’t know how to construct even the most basic mathematical model — even a simple regression is a model (the non-random relationship of some variable to another). The good thing about even these simple models is that it is fairly straightforward to interpret the ‘strength’ of the relationship, in other words, how much variation in one thing can be explained by variation in another. Provided the relationship is real (not random), and provided there is at least some indirect causation implied (i.e., it is not just a spurious coincidence), then there are many simple statistics that quantify this strength — in the case of our simple regression, the coefficient of determination (R2) statistic is a usually a good approximation of this.

In the case of more complex multivariate correlation models, then sometimes the coefficient of determination is insufficient, in which case you might need to rely on statistics such as the proportion of deviance explained, or the marginal and/or conditional variance explained.

When you go beyond this correlative model approach and start constructing more mechanistic models that emulate ecological phenomena from the bottom-up, things get a little more complicated when it comes to quantifying the strength of relationships. Perhaps the most well-known category of such mechanistic models is the humble population viability analysis, abbreviated to PVA§.

Let’s take the simple case of a four-parameter population model we could use to project population size over the next 10 years for an endangered species that we’re introducing to a new habitat. We’ll assume that we have the following information: the size of the founding (introduced) population (n), the juvenile survival rate (Sj, proportion juveniles surviving from birth to the first year), the adult survival rate (Sa, the annual rate of surviving adults to year 1 to maximum longevity), and the fertility rate of mature females (m, number of offspring born per female per reproductive cycle). Each one of these parameters has an associated uncertainty (ε) that combines both measurement error and environmental variation.

If we just took the mean value of each of these three demographic rates (survivals and fertility) and project a founding population of = 10 individuals for 1o years into the future, we would have a single, deterministic estimate of the average outcome of introducing 10 individuals. As we already know, however, the variability, or stochasticity, is more important than the average outcome, because uncertainty in the parameter values (ε) will mean that a non-negligible number of model iterations will result in the extinction of the introduced population. This is something that most conservationists will obviously want to minimise.

So each time we run an iteration of the model, and generally for each breeding interval (most often 1 year at a time), we choose (based on some random-sampling regime) a different value for each parameter. This will give us a distribution of outcomes after the 10-year projection. Let’s say we did 1000 iterations like this; taking the number of times that the population went extinct over these iterations would provide us with an estimate of the population’s extinction probability over that interval. Of course, we would probably also vary the size of the founding population (say, between 10 and 100), to see at what point the extinction probability became acceptably low for managers (i.e., as close to zero as possible), but not unacceptably high that it would be too laborious or expensive to introduce that many individuals. Read the rest of this entry »

It’s not always best to be the big fish

3 02 2016

obrien_fish_2Loosely following the theme of last week’s post, it’s now fairly well established that humans tend to pick on the big species first.

From fewer big trees, declines of big carnivores, elephant & rhino poaching, to fishing down the web, big species tend to cop it hardest when it comes to human-caused ecological disturbance.

While there are a lot of different combinations of traits that make some species more vulnerable to extinction than others (see examples for legumes, amphibians, sharks & teleosts, and mammals), one of the main ones is species size.

Generally speaking, larger species tend to produce fewer offspring and breed later in life than smaller species. This means that despite larger species tending to live longer than their smaller counterparts, their ‘slow’ reproductive output means that they are generally more susceptible to rapid environmental change (mainly via human intervention). In other words, their capacity for self-replacement is often too low to counteract the offtake from direct exploitation or habitat loss.

Despite a reasonable scientific understanding of this extinction-risk principle, the degree to which human disturbance affects species’ distributions is much less well quantified, and this is especially true for marine species.

I’m proud to announce another fascinating paper led by my postdoc, Camille Mellin, that has just come out online in Nature CommunicationsHumans and seasonal climate variability threaten large-bodied coral reef fish with small ranges.

With the world’s largest combined dataset of coral reef fish surveys for the entire Indo-Pacific (including the coral reef fish biodiversity hotspot — the Coral Triangle), we examined which conditions best described the distribution of fishes over a range of body sizes. Read the rest of this entry »

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