Lose biodiversity and you’ll get sick

14 03 2014

dengueHere’s a (paraphrased) recommendation I did recently for F1000 about a cool avenue of research I’ve been following for a few years now. Very interesting, but much, much more to do.

The core concepts of conservation ecology are well-established: we know that habitat lossfragmentation, invasive species, over-exploitation and of course, climate change, are bad for biodiversity. This well-quantified scientific baseline has led the discipline recently to embark on questions pertaining more to the (a) implications of biodiversity loss for humanity and (b) what we can do to offset these. A recent paper by Morand and colleagues addresses perhaps one of the most compelling reasons that human society should appreciate biodiversity beyond its intrinsic value; as biodiversity degrades, so too does human health.

Some argue that the only way to convince society in general that biodiversity is worth protecting is that we link its loss directly to degrading human health, wealth and well-being. Confirmation of such relationships at a variety of spatial and temporal scales is therefore essential. Morand and colleagues used data from a variety of sources to test two predictions: (1) that the number of infectious disease should increase as overall biodiversity increases and (2) that biodiversity loss, inferred from species threat and deforestation data, should increase the number of infectious disease outbreaks in humans. Using data from 28 countries in the Asia-Pacific region, they confirmed both predictions.

While the authors rightly controlled for various confounding effects such as population density, country area and health investment, their statistical approaches were basic and potentially prone to misinterpretation. While I’m reasonably confident that their overall conclusions would hold, it would be prudent to re-analyse the dataset using more sophisticated methods (e.g., accounting for spatial autocorrelation and model uncertainty). It would also be prudent to expand the rather small sample size to more than 28 countries.

These analytical issues aside, the potential mechanisms underlying the correlative phenomena are interesting. While it’s not unexpected that pathogen diversity should increase as overall biodiversity increases (more diversity, full stop), it is ecologically fascinating how biodiversity degradation could lead to a higher incidence of infectious disease in humans. Two mechanisms are proposed. One is the direct ‘dilution’ effect where a high number of potential hosts reduces the chances that any one (including humans) becomes infected with the pathogen. Another is the indirect dilution effect whereby higher host diversity reduces susceptible host density via intensified interspecific competition. Clearly the mechanisms underlying the correlations require much more work; regardless, the paper’s message represents an essential piece in the ecosystem services puzzle.

CJA Bradshaw



7 responses

8 05 2017
Who are the healthiest people in the world? | ConservationBytes.com

[…] topic is on human health, which as I’ve written many times before, is in many ways linked to the quality of the environment in which people live. We are currently looking at which countries have the best human health […]


25 03 2014

Reblogged this on for Biodiversity's sake!.


17 03 2014
If biodiversity is so important, why is Europe not languishing? | ConservationBytes.com

[…] Even rarer is devoting an entire post to answering a question. The other day, I received a real cracker, and so I think it deserves a highlighted […]


15 03 2014

Fascinating article. I appreciate your analysis of the study’s findings and the further work that needs to be done. It seems a small subset of the public appreciates the “intrinsic value” argument for protecting biodiversity. That means that for most people and agencies we have to show direct value to humans of biodiversity in general. I’m glad that more researchers are realizing this and taking up the cause. I predict some of the gaps in the public’s knowledge will still leave the rhetorical question “what’s the worth of [insert any singular species]?” unanswered. But perhaps we’re moving past the age of needing charismatic megafauna to grab people’s hearts; if we’re also expressing the financial and health costs of biodiversity loss, more people will listen.


15 03 2014
P. Basu

I am an Indian who lived in Germany for quite a long period. Now, if I am not grossly mistaken, once upon a time Germany and other west european countries had large tracts of “real” forests with bears, wolves, foxes and other animals (both carnivore and herbivore). Bear has completely disappeared from these countries with the advent of industrialization. A few wolves have been kept in more or less artificially created forests. Foxes, deer and hares, fortunately, do still exist. My question is, how come these countries are still so well off – not only from the point of view of economy but also from the angle of public health despite the loss of large tracts of natural forests? Or is it that modern science and a health conscious society can compensate the loss of biodiversity.


14 03 2014
Garry Jolley-Rogers

interesting arguments which are obvious when I think about it. I agree with Graeme not an antidote to preserve biodiversity. Sadly, its a small counterweight against more manifest short term interests. However, it does pose interesting questions worthy, I think, of further work. Perhaps, much like why some things are weedy/invasive? and that could be useful in the fight to preserve biodiversity vs global homogeneity.


14 03 2014
Graeme McLeay

Thank you Corey, this is a fascinating topic,and is partly covered in Peter Doherty’s book “Sentinel Chickens” which looks at the role birds play in human health and how habitat loss, climate change, and monocultures influence those interactions. It seems humans will only act when self interest forces them to do so.


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