From protists to whales: predicting the future of biological systems

Complex biological systems are notoriously unpredictable, but forecasting their fate has arguably never been more important. In a recent seminar in the School of Biological Sciences, Dr. Chris Clements describes his latest research in this emerging field at the interface of ecology and conservation science.

The world is facing an unprecedented biodiversity crisis. As mankind’s ecological footprint grows ever larger, the rate of environmental change continues to accelerate. Identifying at-risk populations or ecosystems before they are irretrievably lost or damaged is becoming an increasingly important goal for conservationists, but predicting how complex biological systems will respond to evolving pressures is challenging.

One way of forecasting the future trajectory of biological systems is to use system-specific models founded on a detailed understanding of the underlying ecological processes. In practice however, scientists’ ability to do this is constrained by a scarcity of in-depth knowledge for the vast majority of ecosystems. An alternative strategy is to concentrate on inferring changes in the underlying state of the system from trends in more readily available data, such as estimates of population abundance. This approach is based on detecting statistical patterns or ‘early warning signals’, which can potentially be used to alert conservationists to the imminent danger of a sudden and catastrophic shift within an ecosystem, or the impending collapse of a population. A large part of Dr. Clements’ current research is focused on testing and extending these techniques.

“Under sustained pressure, the system will eventually reach a tipping point where it is so unstable that even tiny disruptions can trigger an abrupt change”

Dramatic shifts within ecosystems can occur when a change in conditions overwhelms the capacity of the system to return to its original state. Under sustained pressure, the system will eventually reach a tipping point where it is so unstable that even tiny disruptions can trigger an abrupt change. A classic example is the rapid transformation of pristine coral reefs due to declines in the abundance of algae-grazing marine life. While transitions to so-called ‘alternative stable states’ are often difficult to reverse, in theory, it should be possible to detect them in advance: as tipping points approach, predictable changes in statistical signals should become apparent.

Despite the potential usefulness of abundance-based early warning signals, the inherently noisy nature of population estimates can sometimes lead to unreliable predictions. Animals living in complex and inaccessible landscapes are usually elusive, and it can be tricky to estimate population sizes with confidence. One possible solution to this problem is to combine or replace abundance-based early warning signals with information on trends in key individual traits, such as body size, which can be estimated more reliably. Crucially, shifts in the distribution of body sizes within the population at-risk can be indicative of deteriorating environmental conditions, and of a population under strain.

“Dramatic shifts in the variability of body size also predicted plummeting worldwide populations of blue, fin, sei and sperm whales during the historical period of commercial whaling”

By describing his recent experiments on microcosm populations of the predatory protist Didinium nasutum, Chris showed that the collapse of stressed populations was preceded by a sharp decline in mean body size. Switching focus to an analysis of whale populations during the 20th century, Chris went on demonstrate how dramatic shifts in the variability of body size also predicted plummeting worldwide populations of blue, fin, sei and sperm whales during the historical period of commercial whaling. In both cases, trait-based early warning signals produced more accurate predictions about timing of population collapses, compared to those based on measures of abundance.

While our understanding of trait-based early warning signals is progressing rapidly, there is still much to learn about how these techniques can be applied to identify at-risk biological systems in the real world, where populations differ markedly in the rate of environmental change they are exposed to. Using both mathematical models and experimental microcosms, Chris’s research group is currently focused on tackling a range of unresolved questions in this area.

Written by Andrew Szopa-Comley, PhD student in Biological Sciences



A Day in the Life: Head of School

Day in the Life interview with Head of School Professor Mike Benton

Professor Mike Benton
  • What do you normally do before work?

My ideal breakfast would be a kipper or a haggis, but I don’t usually get that I must admit, so a leisurely breakfast where I read the paper, do the crossword and come to work.

  • What is the first thing that you do when you arrive at the LSB?

I kill emails when I arrive. There are usually around 50 emails that have come in, I get these down very quickly, so I apologise to anybody if they have sent an email first thing, I just skim past it with all the spam and all the other stuff that comes through. I then look through my diary to see what is coming up and prepare for meetings, lectures and things like that.

  • Briefly, describe a typical day at work and any interesting things to point out that other members of staff may not know.

It is very difficult to say, and I think everybody will say that there is no such thing as a typical day.

I manage to keep some days clear for research. It is a huge pleasure to be able to get on with projects such as working on mass extinctions, dinosaurs, and all the things I love to do. I often speak to students, masters and PhD’s to find out how they are getting on and to help with their writing, planning, booking visits to museums and those kinds of things.

But at the moment being head of the department I attend a lot of meetings and I have to ask people what on earth all these meetings are. I try to delete as many of them as I can, I go to things and sit there and wonder why I am there sometimes, but there is often an opportunity to speak up for the School of Biological Sciences, so I always do that.

  • What is your favourite part of the day?

I guess my favourite part of the day is after 17:00 because then things become quiet. If you stay on until 18:00 then that is an hour without meetings and without people knocking on the door, a very good moment.

  • Tell us an interesting fact about yourself?

Because I do a lot of fieldwork in China, I go to China maybe once or twice a year and of course being polite one eats what one is given so I have eaten a variety of turtles or terrapins I suppose they are. The most unusual thing I have had to eat was a bit of the larynx of a cow which was a bit like eating a sort of faintly meaty plastic.

  • What is your favourite way to spend your weekends/favourite hobbies?

At the weekend I love to be in my garden which has lots of trees. I love climbing around in the trees when my wife is out and trimming them and cutting the huge hedges, and generally just gardening is a nice fun thing to do.

  • If you could go to any place in the world, where would you go?

I would love to go to Antarctica sometime, I have never been there, and I think many people would say the same. I suppose it is kind of easier to get to every other continent and I have been to every other continent as it happens, but Antarctica would be fun. It’s cold and full of penguins – what could be better than that?

  • Finally, tell us why you love working here!

Well, I love working at the University of Bristol in the Life Sciences building, because you can do what you like. I just love it. I come and go when I like and do what I like and I am getting paid to do my hobby; it’s fantastic.