Tag Archives: E O Wilson

Ten papers that shook my world – watching empty islands fill up – Simberloff & Wilson (1969)

Sadly this is the tenth and last in my series of the ten papers that had a great influence on my life as an ecologist.  I’m going to cheat somewhat and actually discuss three papers. In my defence they are extremely closely linked and I am pretty certain that in today’s publishing world they would all have had to have been combined anyway.  That aside, I really liked this experiment the first time I read about it and still rate it very highly.  I would, however, love to be able to travel back in time and give them a couple of hints with the benefit of hind-sight, although as the authors are two of the greatest living ecologists, Dan Simberloff and E O Wilson, I might be a bit apprehensive doing so 🙂 In any case, much of what I would have said was addressed a few years later (Simberloff, 1976).

Wilson and Simberloff wanted to practically test the island biogeography theory famously described by McArthur and Wilson a few year earlier (MacArthur & Wilson, 1967).  To do this they travelled to the Florida Keys and after due reconnaissance decided that the many mangrove “tree islands” would be ideal study sites (Figure 1).  Then came the really cool bit.

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Figure 1.  Two of the experimental ‘islands’ from Wilson & Simberloff (1969)

They set about removing the arthropod animal life from nine of the islands (Figure 2), or as much as they could, by fogging with methyl bromide; not something we could do now.  They then monitored the islands at frequent intervals for the next year.  They had of course surveyed the islands before they fumigated them.

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Figure 2.  What a cool project; defaunation in progress – from Wilson & Simberloff (1969)

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Figure 3. Island equilibria – from Simberloff & Wilson (1970)

The major finding from their study was that recolonization happened quite quickly and that a year later had pretty much reached an equilibrium position (Figure 3).  Another important finding and one that has important implications for restoration and conservation strategies was that two years after the defaunation event, although the islands were well populated, the species composition, except for one island was less than 40% similar to the original inhabitants (Simberloff & Wilson (1970).  Most species present were new to those islands.  The analysis of the data presented in the two data papers is rather basic, some of the key island biogeographical premises are not addressed at all and I wondered why they had not done so.  Their data are all shown in some detail so it is possible to do some more analysis, which I took the liberty of doing.  The extra analysis shows why they did not discuss area effects per se .  The only significant relationship that I could find was that between the number of species and the distance from the ‘mainland’ source (Figure 4), which as predicted by MacArthur & Wilson (1967) was negative. Sadly, island size did not correlate with species number (Figure5).   Finally, there was a positive, but not significant relationship between the initial number of species found on an island and the number a year later (Figure 6).

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Figure 4.  Relationship between distance from ‘mainland’ source and the number of arthropod species present (R2 = 0.65, P <.0.05) Data from Simberloff & Wilson (1970).

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Figure 5.  Island diameter and number of arthropod species (not statistically significant, r2 = 0.19, although I am sure many politicians would view this as a positive trend). Data from Simberloff & Wilson (1970)

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Figure 6.  Initial number of species on an island and number of species present one year later. Although it looks convincing (r2 = 0.54), there are too few observations to reach statistical significance.  Data from Simberloff & Wilson (1970)

Although this work was extremely influential, (my Bracknell roundabouts study owes a lot to it), there were two major flaws in the original experimental design.  Firstly the number of islands was very low, but of course this is understandable, given the effort and complex logistics required to remove the arthropods safely (Figure 2).  The other flaw was that the islands did not cover a large enough range of sizes, thus making it less likely for the species-area pattern to be detected which was a great shame.

As I mentioned earlier, these short-comings were not ignored by the authors, and a few years later Sinberloff (1976) reported the results of an enhanced study, again in the Florida Keys, where he was able to convincingly demonstrate the species-area effect.   I guess that this was pretty satisfying as it tied up a number of loose strings.  He also managed to get the phrase “flogging a dead horse” into his introduction 🙂

Of the three papers, Simberloff & Wilson (1969) is the most highly cited (according to Google Scholar, 618 to date) and became a “citation classic”* in 1984 at which time it had accumulated 164 citations.  Simberloff & Wilson (1970) has attracted 252 cites with Wilson & Simberloff (1969) trailing in third with a mere 158 cites.  As a point of interest, Simberloff (1976) has so far received 313 cites.  To reiterate, the original mangrove island study, despite its flaws was a fantastic piece of work and Sinberloff and Wilson won the Mercer Award of the Ecological Society of America for this work in 1971.

I can think of no better person to explain why Simberloff & Wilson (1969) deserves its place in the Ecological Hall of Fame than Simberloff himself who in the commentary to the 1984 citation classic article wrote “I think the main reason it is cited, however, and its lasting contribution, is not so much that it supports the [equilibrium] theory, as that it reported a field experiment on ecological communities, and thus seemed dramatically different from the correlative approach that dominated this field

 

References

MacArthur, R.H. & Wilson, E.O. (1967) The Theory of Island Biogeography Princeton University Press, Princeton.

Simberloff, D. (1976)  Experimental zoogeography of islands: effects of island size.  Ecology, 57, 629-648.

Simberloff, D. & Wilson, E.O. (1969) Experimental zoogeography of islands: the colonization of empty islands. Ecology, 50, 278-296.

Simberloff, D. & Wilson, E.O. (1970) Experimental zoogeography of islands: a two-year record of colonization. Ecology, 51, 934-937.

Wilson, E.O. & Simberloff, D. (1969) Experimental zoogeography of islands: defaunation and monitoring techniques. Ecology, 51, 267-278.

 

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Reflections on the dawning of the Anthropocene

We are now officially in the Anthropocene Age which is probably not a good thing.  It seems an appropriate moment to reflect on what we can do to halt, or at the very least, slow down, what seems to be an unstoppable race to extinction of most of the natural world.  We all know what the principal causes are despite the obfuscation and prevarication that surrounds the debate. Equally, we are also aware of the mainly political and economic pressures that are preventing us from doing something to ease the pain and suffering we are inflicting on the world. I am not going to rehearse the arguments, but instead I will let the following speak to us all about why we need to keep and enhance what nature we have remaining.

Anthropocene

“Though large herds of deer do much harm to the neighbourhood, yet the injury to the morals of the people is of more moment than the loss of their crops.  The temptation is irresistible; for most men are sportsmen by constitution: and there is such an inherent spirit for hunting in human nature, as scarce any inhibitions can restrain” Gilbert White (1788)

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They didn’t know any better – Passenger pigeon flock being hunted in Louisiana (Credit: Smith Bennett, 1875/Public domain.)

Anthropocene 2.GIF

They should know better – mind boggling and shocking

“Really I did deserve a chastisement for my intrusion into the meadow, the disastrous consequences of which I now had power to perceive to the full extent. I had bruised the tender stalks of springing grass, broken quantities of buds, and destroyed myriads of living creatures. In my stupid simplicity I had never had any suspicion of the pain I caused while perpetrating these evil deeds, and had been in a state of delight at the profound peace pervading the country, and the charms of solitude” E van Bruyssel (1870)

Anthropocene 3.

“We can never afford to lose sight of past and present human activities in their effects on the vegetation of countries which have been long inhabited and densely populated, like those of Western and Central Europe” A G Tansley (1923)

“On the favourable side of the balance, I think that I am superior to the common run of men in noticing things which escape attention, and in observing them carefully.  My industry has been great as it could have been in the observation and collection of facts.  What is far more important, my love of natural science has been steady and ardent” Charles Darwin (1929*)

“We have tried to conquer nature by force and by intellect.  It now remains for us to try the way of love It is impossible to use the full resources of the soil except with a mixture of plants (either grown together as in pasture or mixed crops grown in succession as a in a proper rotation of crops).  In monoculture it is impossible to keep disease at bay for long, and in addition it is impossible to feed animals properly except on a varied mixture” Lord Northbourne (1940)

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“The soil is among Nature’s greatest marvels. A clod of earth, seeming simple and lifeless, is now known to be highly complex in structure, its particles most elaborate in their composition, with numerous invisible crevices inhabited by prodigious numbers of living organisms inconceivably small, leading lives of which we can from only the haziest conception, yet somehow linked up with our lives in that they produce the food of plants which constitute our food, and remove from the soil, substances that would be harmful to us” Sir John Russell (1957)

“Over increasingly large areas of the United States, spring now comes unheralded by the return of the birds, and the early mornings are strangely silent where once they were filled with the beauty of bird song” Rachel Carson (1962)

“I believe the strongest argument for keeping as much of the natural world as possible in the anthrosphere lies in the human need for variety, individuality, and the challenge of endeavouring to understand the nonhuman world.  I believe, too, that emersion in the world of trees, flower, and wild creatures is needed to nourish human attributes now in short supply: awe, compassion, reflectiveness, the brotherhood we often talk about but rarely practice except on the most superficial of levels”  Howard Ensign Evans (1966)

Epping

“I have heard it said more than once that the reason why there are more wire-worms afflicting the crops than in the past is that there are more tractors. The idea being that since the tractor-driven plough turns over three or four furrows at a time as against the horse-plough’s one furrow, the results is that birds get far fewer troughs in which to find worms,  Thus more worms are left in the soil.  It is an attractive theory, there is something cheering in the knowledge that Nature always hits back.  Everything in nature has a meaning and a purpose.  Everything is necessary to the universal scheme, every germ, every microbe, every pest.  When anything ceases to serve the harmony it dies out” John Stewart Collis (1973)

“Humanity now co-opts something in the order of one-twentieth of all the photosynthesis – the primal driving process of life on the planet – for its own uses.  And through its activities, Homo sapiens now threatens to alter the basic climatic patterns of the globe” Paul & Anne Ehrlich (1981)

“The rescue of biological diversity can only be achieved by a skillful blend of science, capital investment, and government: science to blaze the path by research and development; capital investment to create sustainable markets: and government to promote the marriage of economic growth and conservation” Edward Wilson (1992)

“Despite what developers will tell you about restoration, she said, once a piece of land is graded, the biologic organisms and understructure of the soil are destroyed.  No one knows how to really re-create that, short of years of hand-weeding.  Leaving land doesn’t work; the natives are overwhelmed by the invaders” Richard Louw (2005)

“Eventually some truth dawned: nature conservation is essentially concerned with mending the relationship between people and Nature, and is an expression of love for, and an interaction with, the beauty and wonder of the natural world, and with belonging in Nature” Matthew Oates (2015)

Enjoying Malham

“Evidence shows that loss of interactions with nature changes people’ s attitudes toward nature, including the values they place on it, their beliefs concerning the environment, their perceived norms of environmental ethics, and their willingness to protect nature” Soga & Gaston (2016)

I could go on, and on, but I think you get the picture.  We could have done so much so earlier.

Please share your favourite passages, be they gloomy or optimistic, by adding them to the comments.

 

References

Carson, R. (1962) Silent Spring, Houghton Mifflin, USA.

Collis, J.S. (1973)  The Worm Forgives the Plough. Penguin Books

Darwin, C.  (1929) Autobiography of Charles Darwin, Watts & Co., London (

*published posthumously)

Ehrlich, P.  & Ehrlich, A. (1981) Extinction, Random House, New York.

Evans, H.E. (1966)  Life on a Little-Known Planet, University of Chicago Press, USA.

Louw, R. (2005)  Last Child in the Woods, Atlantic Books, London.

Northbourne, W.J. (1940) Look to the Land, J.M. Dent & Sons.

Oates, M. (2015) In Pursuit of Butterflies: A Fifty-Year Affair, Bloomsbury, London.

Russell, Sir, E.J. (1957) The World of the Soil, Collins, London.

Soga, M. & Gaston, K.J. (2016) Extinction of experience: the loss of human–nature interactions.  Frontiers in Ecology and the Environment, 14, 94-101

Tanlsey, A.G. (1923) Introduction to Plant Ecology, George Allen & Unwin Ltd.

Van Bruyssel, E. (1870) The Population of an Old Pear Tree, MacMillan & Co. London

White, G. (1788) The Natural History of Selborne, Penguin Edition 1977.

Wilson, E.O. (1992) The Diversity of Life, The Belknap Press of Harvard University Press, USA.

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