Monthly Archives: September 2012

The grass is always greener

Andrew Hendry critiques the ecosystem services argument for biodiversity preservation.

I suspect that weak and inconsistent relationships between biodiversity and ecosystem function are symptomatic of the reality that biodiversity also provides ecosystem disservices.  Some species are just flat-out bad for clean water, productivity, nutrient cycling, and pollination. And, of course, many species are unequivocally bad for humans in general, most obviously a number of diseases. So perhaps we have, on the one hand, a positive relationship between biodiversity and good aspects of ecosystem function (services) but also, on the other hand, a negative relationship between biodiversity and bad aspects of ecosystem function (disservices).

Brian McGill thinks ecologists often use statistical methods they shouldn’t.

In my experience ecologists have a long list of “must use” approaches to statistics that are more complicated than simpler methods but don’t necessarily change the outcome. To me this is a machismo attitude to statistics – “my paper is better because I used tougher statistics”. It has a Red-Queen dynamic – eventually what starts as a signal of being superior turns into something reviewers expect in every paper. But often times with a little thinking, there is really no reason this analysis is needed in a particular case (the reviewer who is requiring it is so far removed from the development of the approach that they have forgotten why it is really used). And even if the more complex approach might be relevant, it can be very costly to implement but often have very little impact on the final results. Thus what started out as statistical machismo turns into wasted time required by reviewers.

John Morgan gives a little attention to the first step in the scientific process.

At any new site I visit, I have a little checklist of things I ask myself: how does the topography change? How does the overstorey change? How does the understorey change? How does the soil change? By running through this list, I can start to arrange the components of the landscape into some sort of order. My geomorphologist friend Neville Rosengren calls this ‘being able to read the landscape’. While he’s looking at rocks and landforms, such a concept is equally applicable to the vegetation.

What does a paper on air pollution have to do with pollen movement?

Air pollution reduces visibility in Benxi, China. Photo by Susannah Tysor.

Recently, some mathematicians at Arizona State and Notre Dame modeled how wind moves pollutants around in a city. Liat Clark summarizes their findings nicely. Basically, if you look at air movement over a long period of time, you find that most of the pollution ends up in a few predictable places. This is important for city planning – if you can figure out how the physical structure of your city interacts with the wind to distribute pollution in the city, you can prevent or fix pollution ‘hotspots.’

I’m studying pollen, not air pollution. But the technique this paper uses could be very useful for me. Like air pollutants, pollen are tiny particles carried along by the wind. I’m trying to figure out how similar patterns of pollen travel are every year – does population A send pollen to population B every year, every 10 years, every 50 years, never? This paper suggests that at least at small scales (the size of a city), pollen movement will be highly structured and similar year to year.

The geometry of inertial particle mixing in urban flows, from deterministic and random displacement modelsPhys. Fluids 24, 063302 (2012)