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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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 »

Get serious about divestment

21 11 2014

dh-logo1We are a sensitive and conflict-avoiding lot, aren’t we? Most scientists I know absolutely dread reprisals of any form, whether they are from a colleague commenting on their work, a sensationalism-seeking journalist posing nasty questions, or a half-wit troll commenting on a blog feed. For all our swagger and intellectual superiority complexes, most of us would rather lock ourselves in a room and do our work without anyone bothering us.

Fortunately for the taxpayer, we should not and cannot be this way. As I’ve stated before, we have at the very least a moral obligation to divulge our results to as many people as possible because for the most part, they pay us. If you work in any applied form of science (most of us do) – such as conservation, for example – then your moral obligation to make your work public extends to the entirety of humanity and the planet. That’s a staggering responsibility, and one of the reasons I’ve embraced many other forms of communication beyond the bog-standard scientific publication outlets.

There are many great examples of impressive science advocates out there – a few that come to mind are people like inter alia Lesley Hughes, James Hansen, Michael Mann, Paul Ehrlich, Bill Laurance, Barry BrookOve Hoegh-Guldberg, Tony Barnosky, Gretchen Daily, Emma Johnston, Stuart Pimm, and Hugh Possingham. There are even others willing to go to extraordinary lengths to make an evidence-based protest against society’s more inane actions. I’ve said it before, but it bears repeating – evidence-based advocacy can work.

To the topic at hand – I’ve been a little disappointed – to say the least – with the near-total silence emanating from my colleagues about the fossil-fuel divestment wave sweeping the world. While gaining traction worldwide, it wasn’t until The Australian National University took the bold move to divest (at least partially) from many of its fossil-fuel financial interests that it became a reality in Australia. Let’s face it – of all the types of institutions in our world, universities should be at the forefront of good, morally grounded and socially responsible investment strategies. They are, after all, meant to be filled with the most erudite, informed and cutting-edge people in the world, most of whom should have the best information at their fingertips regarding the precarious state of our environment. Read the rest of this entry »

Terrestrial biodiversity’s only chance is avoided deforestation

24 01 2014

farming forestsToday I was shocked, stunned and pleasantly (for a change) surprised. Australia has its first ‘avoided deforestation’ carbon farming project.

It is understandable that this sort of news doesn’t make the Jane & Joe Bloggs of the world stand up and cheer, but it should make conservation biologists jump for bloody joy.

So why exactly am I so excited about the setting aside of a mere 9000 ha (90 km2, or 10 × 9 km) of semi-arid scrub in western New South Wales? It’s simple – nothing can replace the biodiversity or carbon value of primary forest. In other words, forest restoration – while laudable and needed – can never achieve what existing forest already does. We know now from various parts of the world that biodiversity is nearly always much higher in primary forest, and that the carbon structure of the forest (especially below-ground carbon) can take centuries to recover.

Another problem with restoration – and if you’ve ever been involved in any tree planting yourself, you’ll know what I mean – is that it’s incredibly expensive, time-consuming and slow. Wouldn’t it make more financial sense just to save forests instead of trying to rebuild them?

Of course it is, so the logical conclusion from a conservation perspective is to save primary forest first, then worry about restoration next. The problem is, there are few, if any, financial incentives for keeping forests standing in the private sector. The stumbling rise of the carbon economy is a potential resolution to this problem, although neither the Kyoto Protocol nor most national carbon-trading schemes adequately account for the carbon value of existing forests.

Up until today, even Australia didn’t have any examples.

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Australia’s national parks aren’t ‘national’ at all

14 06 2013

Yarra-Ranges-National-Park-AustraliaFollowing our The Conversation article a few weeks ago about the rapid demise of national parks in Australia, a few of us (me, Euan Ritchie & Emma Johnston) wrote a follow-up piece on the Australia’s national park misnomer (published simultaneously on The Conversation).

Australia boasts over 500 national parks covering 28 million hectares of land, or about 3.6% of Australia. You could be forgiven for thinking we’re doing well in the biodiversity-conservation game.

But did you know that of those more than 500 national parks, only six are managed by the Commonwealth Government? For marine parks, it’s a little more: 61 of the 130-plus are managed primarily by the Commonwealth. This means that the majority of our important biodiversity refuges are managed exclusively by state and territory governments. In other words, our national parks aren’t “national” at all.

In a world of perfect governance, this wouldn’t matter. But we’re seeing the rapid “relaxation” of laws designed to protect our “national” and marine parks by many state governments. Would making all of them truly national do more to conserve biodiversity?

One silly decision resulting in a major ecosystem disturbance in a national park can take decades if not hundreds of years to heal. Ecosystems are complex interactions of millions of species that take a long time to evolve – they cannot be easily repaired once the damage is done.

Almost overnight, Queensland, New South Wales and Victoria have rolled back nearly two centuries of park protection. What’s surprising here is that many of our conservation gains in the last few decades (for example, the Natural Heritage Trust, the National Reserve System, the Environment Protection and Biodiversity Conservation Act and a national marine reserve network) originated from Coalition policies. Read the rest of this entry »

The invisible hand of ecosystem services

4 08 2012

I’ve just spent nearly an entire week trying to get my head around ecosystem services (ES).

You’d think that would have been a given based on my experience, my research, my writings and the fact that I’ve just spent the last week with 400 ES specialists from around the world at the 5th international Ecosystem Services Partnership (ESP) Conference in Portland, Oregon, USA.

Well, prior to this week I thought I knew what ES were, but now I think I’m just a little more confused.

Of course, I’m not talking about the concept of ES or what they are (hell, I’ve written enough about them on this blog and in my papers); my problem is understanding how we as society end up valuing them in a practical, sensible and feasible way.

So I’m going to describe the ESP Conference as I saw it, and not necessarily in chronological order.

First up is the term ‘ecosystem services’ itself – horrible name, and something rammed home again after attending the conference. Most people on the planet that are not scientists (that would be nearly everyone) just might have the most tenuous and ethereal of grasps of ‘ecosystem’ in the first place, and I’d bet that 99 % of most undergraduate students couldn’t provide a comprehensive description. This is because ecosystems are mind-bogglingly, chaotically and awesomely complex. Just ask any ecosystem ecologist.

The second part of the term – services – is particularly offensive in its presumption and arrogance. It’s not like you ring up an ecosystem and get it to clean your carpets, or fill your water tank or gas cylinder. No, the natural world did not evolve to pamper humanity; we are merely part of it (and bloody efficient at modifying it, I might add).

So try to sell this ‘incredibly complex thingy’ that is ‘there to do some (intangible) shit for us’ to the public, policy makers and politicians, and you mostly get a dog’s regurgitated breakfast and some blank, slack-jawed stares. Read the rest of this entry »

Arguing for scientific socialism in ecology funding

26 06 2012

What makes an ecologist ‘successful’? How do you measure ‘success’? We’d all like to believe that success is measured by our results’ transformation of ecological theory and practice – in a conservation sense, this would ultimately mean our work’s ability to prevent (or at least, slow down) extinctions.

Alas, we’re not that good at quantifying such successes, and if you use the global metric of species threats, deforestation, pollution, invasive species and habitat degradation, we’ve failed utterly.

So instead, we measure scientific ‘success’ via peer-reviewed publications, and the citations (essentially, scientific cross-referencing) that arise from these. These are blunt instruments, to be sure, but they are really the only real metrics we have. If you’re not being cited, no one is reading your work; and if no one is reading you’re work, your cleverness goes unnoticed and you help nothing and no one.

A paper I just read in the latest issue of Oikos goes some way to examine what makes a ‘successful’ ecologist (i.e., in terms of publications, citations and funding), and there are some very interesting results. Read the rest of this entry »