Demons in Eden

Book Review by Norman Todd February 2006

This is a book I recommend you read. I found it fascinating and frightening. Jonathan Silvertown is a professor of ecology who, in this book, attempts to give some explanation for the Darwinian paradox that if evolution is driven by the survival of the fittest why, in the plant world at any rate, are there about 400,000 species? Further, is there, to use his phrase, a ‘Darwinian Demon’ — a super-organism — waiting to swamp and conquer these 400,000 species? Our species, homo sapiens, has caused major changes to occur in about 40% of the world’s land surface. Have we become the ‘Darwinian Devil’?

Silvertown is the author or editor of a number of previous books and I found it eerily significant that he states in his preface that finding a publisher for Demons in Eden was an “endurance test requiring the tenacity of a hardy perennial”. This book is certainly a call to arms but Silvertown’s approach is not just a tree hugger’s tirade. I was persuaded by the logic of his observations and his adherence to scientific standards. The environment is being degraded incrementally. So what if another one or two, largely unknown, plants disappear every day? No one person or group or nation is responsible and it is not only ‘economy versus environment’ that is causal. It is our own perceived need for survival — on an ever-increasingly consumptive scale. [A similar problem exists with human-generated emissions to the atmosphere. There is near unanimity in the scientific world that calamitous climate change is happening and we are causing it but the message is not being heard in any practical sense and, worse, is being denied and largely ignored].

Silvertown starts out with a current account of the green part of the ‘Tree of Life’. The concept of showing the evolution of life-forms in the shape of a tree is a Darwinian one. In fact the only diagram in The Origin of Species is a schematic ‘tree’. A particular part of Darwin’s 1859 tree has now been redrawn using the molecular systematics of DNA. This part of the book describes the relationships among the flowering plants — the angiosperms. [The 2006 winter edition of our Rhododendron Journal has an article showing how Ben Hall, and some of his students used this powerful kind of analysis to show the relationship of the various groups of R. macrophyllum growing on the west coast of our continent]. The ‘Tree of Life’ story, as told by Silvertown, is short but complex. It has resulted from the collaborative work of forty-two scientists. Would you like to know the name of the plant at the base of the tree? It is amborella trichopoda, an almost extinct tree from New Caledonia. Two surprises for me were that the division between dicotyledons [like oaks and rhododendrons] and monocotyledons [like grasses] did not occur at the base of the tree but up quite a way on one branch, and that the second oldest group of plants was the water lilies.

I had never heard of Barro Colorado Island. This is an island of fifteen square kilometers in the Panama Canal on the man-made Gatun Lake. Since 1923 an inventory of every growing shoot has been maintained. On the island there are 365 species of tree, 116 shrubs, 265 climbing plants and 466 herbaceous species. Their life cycles have been traced for over eighty years. Where are the demons? It is true that if you randomly chose one precise spot on the island there is a fifty percent chance of it being occupied by one species of tree. But there are rare plants and they continue to exist. Is rarity a survival mechanism in that it is not worth a predator’s effort to evolve an appetite to use it as a food source? Can there be 1212 different niches that 1212 different plants can exploit? Silvertown quotes Dr. Seuss. I think it is worth repeating.

And NUH is the letter I use to spell Nutches

Who live in small caves, known as Nitches, for hutches.

These Nutches have trouble, the biggest of which is

The fact that there are many more Nutches than Nitches.

Each Nutch in a Nitch knows that some other Nutch

Would like to move into his Nitch very much.

So each Nutch in a Nitch has to watch that small Nitch

Or Nutches who haven’t got Nitches will snitch.

There is a chapter on how small these nitches can be. Near Brighton in the south of England is Castle Hill National Nature Reserve. It is an unremarkable — to the uninitiated — stretch of grassland. Yet typically one square foot of turf will contain thirty different species of flowering plants. Here is the paradox. How can somehow similar species compete with one another and yet coexist? There are still many unanswered questions but you will be rewarded with a better understanding of nitches on reading the book. I was left feeling uneasy about how we grow our rhododendrons. By and large we say, “Give them an acid, humusy soil, lots of water and the ones with the bigger leaves more shade.” Still, despite being ruthless in exterminating rhododendrons’ obvious competition we have many casualties. Read the book; it won’t give you answers but will certainly provide some excuses.

There are other chapters: on the flora of the Canary Islands; on a demon mountain in Japan, [should we be getting a message from the demon bamboo that has learned that you can’t exhaust yourself in procreation and expect not to die in the process?]; on the rampant success of demons in Florida and on pros and cons for genetically modified plants. I was astonished to learn that North America is ten times more welcoming to alien demons than Europe. However, Sivertown cites the devilish success of ‘Rhododendron ponticum’ in Britain. The name is in quotation marks because it is not R. ponticum any longer. The plants of ponticum that were introduced to the U.K. quickly hybridized with R. catawbiense. The latter is a very cold/heat hardy plant. The vigour of the new hybrid was truly demonic and it has laid claim to a nitch as aggressively as broom has here.

Demons in Eden is not a big book; it is only 147 pages but every one of these pages is disturbingly and challengingly provocative. I am about to take a swab from my mouth and send it off to the National Geographic Society. This organization has partnered with IBM in a genographic project. They will analyze my DNA and tell me where I fit on the humanoid ‘Tree of Life’. I am going to receive confirmation of my monkey ancestry — a Darwinian Demon?

Jonathan Silvertown, Demons in Eden (The University of Chicago Press, 2005. ISBN:0-226-75771-4 ).