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Charles Darwin and Biodiversity
From: The British Library
| By:
Andy Hector |
EDITOR'S INTRODUCTION |
Recent experiments exploring the ecological impact of biodiversity were anticipated nearly two centuries ago by the Duke of Bedford's head gardener at Woburn Abbey. When Charles Darwin was writing The Origin of Species he recognised the significance of this work, but the connections with biodiversity research today were only recently pinned down by Dr. Andy Hector, research fellow at Imperial College, London. In an interview with Fathom, Andy Hector relates the curious tale of the gardener, the duke, Charles Darwin and a long-forgotten book re-discovered in the collections of The British Library. |
Fathom: Can you explain how your research in biodiversity led you back to Charles Darwin? |
Andy Hector: Over the last ten or twenty years ecologists have become interested in the loss of biodiversity and in particular the potential impact this could have on our environment, on the way that ecosystems function--how productive and sustainable they are. A lot of research has been done over the last ten years to make a start at answering that question. But in The Origin of Species there's a quote from Darwin where he actually says it has already been experimentally proved that--in essence--if you remove species from ecosystems they will work less well. |
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| Plan of the Hortus Gramineus, or grass garden, at Woburn Abbey in 1817. Reports of the experiments in the garden were noted by Charles Darwin in The Origin of Species. | |
The Origin of Species was written only as an abstract of a longer book. Darwin was working on a work called Natural Selection and then when Alfred Russel Wallace independently formulated the same theory of evolution by natural selection he put that longer book on hold and quickly wrote a joint article with Wallace. Then he wrote The Origin of Species, which he completed in only eight months. He wanted "An Abstract" included in the original title, as that's what it was intended as, but the publishers wouldn't let him get away with that. |
Darwin had been working on this material for many years, holding it back with some concerns over what impact it would have, particularly in religious circles. He'd held it back until he knew that Wallace had come up with the same idea, and then his friends and colleagues said, now you must publish. Of course he had a huge wealth of information that he had developed over those twenty years. But what got left out of The Origin of Species are the sources for the work that he was talking about. So he says that it has been experimentally proved that biodiversity is beneficial for ecosystem functioning. But nobody knew what work he was talking about. So just out of interest, having done similar experiments myself, I went looking to see if I could discover this original work based on a starting point found by my colleague Asher Minns. |
The first place to start was with Natural Selection--the longer but unfinished work. That was really forgotten until the 1950s when there was an article in Science pointing out the existence of this manuscript as a source for additional information. Then the author of that article spent the next twenty years editing together a version of that book from Darwin's notes for publication. That came out in the mid-1970s. So now you can get Charles Darwin's Natural Selection edited by science historian R.C. Stauffer. (Charles Darwin's Natural Selection, being the second part of his big species book written from 1856 to 1858, Cambridge University Press, London, 1995.) |
If you are interested in a particular section of The Origin of Species you need to find the equivalent section in Natural Selection. Luckily enough for us it was there, and there was some additional text from Darwin where he expands on the idea that is really only mentioned as one sentence in The Origin of Species. Even better, this gives the actual source for the experimental work, and that was a magazine for gardeners. |
Darwin used all sorts of sources for the information he gathered together to support his arguments, and gardeners' magazines were one of these sources. In Louden's Gardeners' Magazine he had read an article by a man called George Sinclair who was a fellow of the Royal Horticultural Society ("On cultivating a collection of grasses in pleasure-grounds or flower-gardens and on the utility of studying the Graminaceae", I, 14-29 & 112-116, 1826). There Sinclair presents his work that shows that experimental plots that have more plant species in them are more productive than comparable plots that have fewer species in them. They have lower levels of diversity and lower levels of productivity of yield and so on. |
George Sinclair was also the author of a longer work called Hortus Gramineus Woburnensis (with the sub-title an account of the results of experiments on the produce and nutritive qualities of different grasses and other plants used as the food of the more valuable domestic animals; instituted by John, Duke of Bedford) and basically that's a large book which summarises a whole body of information on experimental work that was done at Woburn Abbey for the Duke of Bedford. George Sinclair was his head gardener and oversaw a lot of this experimental work. |
Fathom: When was Sinclair doing this work? |
Hector: The first edition of Hortus Gramineus Woburnensis was 1816. The experimental work is not actually reported in the first edition but it is in later editions. So the actual work was done somewhere around 1820. The title Hortus Gramineus Woburnensis translates as something like The Grass Garden at Woburn Abbey. |
I was eventually able to track down a copy of this at the British Library in their rare manuscripts collection. The book was commissioned by the Duke but it was also published and even translated into German. The first edition is particularly nice. It's a very large, leather-bound book and inside the front cover you have a large fold-out map with a plan of their experimental garden and a list of exactly what species or varieties or mixtures of species were grown in which plots. And whereas nowadays you would probably have a line drawing or maybe a photograph of the species being discussed, in the first edition they actually had dried pressed specimens of each and every plant species pasted into the book. |
What they had at Woburn was an area of the garden that they had marked off with surrounding hedges. Then inside this they had a large number of experimental plots--242 experimental plots--that were carefully marked out with metal frames and wooden boards set in these frames. They could fill those with any sort of soil they were particularly interested in, and then grow on them any particular species or variety of plants or mixtures of plants. They could then vary the combinations of species and soil that they had and look at how that influenced the performance of the different species. |
Several of the Dukes of Bedford had been very influential in developing agricultural methods and their immediate goal was to try and re-establish species-rich and productive pastures from seed. These were to rival the permanent pasture of long established natural fields. That was their immediate goal. But really the whole work exhibits a much deeper and broader interest in what we would now call the general ecology of plants. It was quite a sophisticated operation as well because they were not only interested in the plants. Humphrey Davey, the famous British chemist, was also involved in performing some of the earliest chemical analysis of the soil and of the plant matter. |
Fathom: Was it unusual during that time for there to be a strong ecological interest? |
Hector: The word ecology wasn't actually coined until the 1860s, and The Origin of Species was published in 1859, so it pre-dates that. It is quite unusual to have such experimental work going on at this time. Most of the early work was probably more observational, so for example, Darwin was interested in trying to explain where all of the biodiversity came from that he observed on his travels around the world. Darwin obviously did experiments himself but probably work on this scale is quite unusual. But in agriculture there was probably more experimental work going on, and this is one of the roots of experimental ecology. |
What they were doing was comparing all sorts of different species or different varieties of the same species grown on these different soils. They were essentially interested in what plants grew where and how well they performed under different situations. They also wanted to know how plants did on their own as compared to interacting when they were put together with other species. A lot of work went on in the experimental garden; this was really just one small part of it. This specific work was a comparison of some species-rich plots which turned out to be very productive with some low diversity plots which turned out to be less productive. |
So this was the source for Darwin's statement that more diverse ecosystems were more productive. Darwin was more interested in trying to explain where diversity came from and how it was maintained: why doesn't one species or just a small number of species take over and exclude everything else? Darwin's argument, to put it simply, is that natural selection leads to the evolution of species that have different ecological niches. But the argument then for why biodiversity could be important for the way that ecosystems function is that then you have different species doing things in different ways so if you lose some species from an ecosystem then you might essentially have these vacant niches. Some of the ecological roles are not being performed and that can be detrimental to how productive and sustainable ecosystems are. That's something we've really only become interested in over the last ten or twenty years. But although it wasn't the main focus of Darwin's interest, I'd argue that he had realised the other side of the coin--that one of the consequences of the evolution of all these differences is that then systems could function better when they had a greater diversity of complementary species in them. |
Fathom: But these ideas weren't seen as significant at the time? Have we really only become attuned to them because of the recent discussion of ecological concerns? |
Hector: I think at the time, for Sinclair and presumably the Duke of Bedford, they had a mixture of agricultural goals, where they were looking to quickly re-establish from seed productive pastures, and also a deeper underlying general biological interest. They were pioneers in this, so there wasn't a good framework for the ideas. They were just doing experiments to see what happened. There are letters from Sinclair to the Duke where he suggests all sorts of other experiments they can do. So I think they were almost playing around, exploring and seeing what results they found. With Darwin there is a much clearer framework for evolution of species differences. At that time, presumably, the loss of diversity probably was not a great concern. It is only in the intervening 200 years, with the accumulative and accelerating loss of biodiversity that we have now come to realise that the loss of diversity could have impacts on ecosystems. Now we are interested in when that will happen and which species are likely to be the ones that have the greatest impact when we lose them. |
Fathom: Was this work picked up by others? Do we know of its influence in any other context? |
Hector: Not as far as I have discovered. I must point out that Darwin's quote was actually first used in a book about the relationship between biodiversity and ecosystem functioning that came out in 1993 from a conference in Germany (Schulze E.-D. & Mooney H.A. Biodiversity and Ecosystem Function, Springer-Verlag, Berlin.) That crystallised this subject area and kick-started discourse on this topic. In a chapter by the ecologist Sam McNorton, he uses the quote in his introduction, and then several other people have picked up on it since. |
Fathom: Can you outline your own experimental work today and how that relates to these issues? |
Hector: What my own research has done over the last few years is to try and answer the question, what is the relationship between biodiversity, numbers of species, and ecosystem functioning? How productive ecosystems are, how sustainable they are. What we have done, as part of a European project, was to do the same experiment in eight different countries around Europe. In these eight different grasslands, we ploughed a field, got rid of the existing vegetation, and marked out experimental gardens--in a similar way to Sinclair--in individual plots. We established new plant communities from seed we'd collected the previous year where we could control the numbers and the types of plant species that we put into them. |
What we found was that--to put it very simply--the plant communities with more species in them were more productive and also functioned better in many other ways as well. They held on to nutrients better, so they may be more sustainable in the longer term. They have greater levels of diversity of associated organisms in the soil or insects above ground and so on. This is really very similar, in many ways, to Sinclair's work, although of course Sinclair's work around 1820 pre-dates all sorts of more modern considerations of experimental design, like replication and randomisation. These concepts hadn't even been invented then. Our work today is similar to what he was doing, but done with more rigorous modern standards. In its basics, however, it is amazingly similar. |
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