The recently published book by Emma Marris, Rambunctious Garden,* is getting the attention it deserves from conservationists and the managers of public lands. If you read widely in this field, as we do, you won’t find much new in her book, but you will find a comprehensive and comprehensible overview of the emerging scientific consensus that it is time to revise the assumptions of invasion biology.
If you haven’t the time or inclination to read this book, you can take a short cut to two recent interviews with Ms. Marris, published by the American Society of Landscape Architects and the magazine of the Nature Conservancy. The published interview by the Nature Conservancy is another indication that this prestigious organization is shifting its emphasis to embrace the realities of nature as we know it, rather than as we imagine it was in the distant past.
Ms. Marris methodically revisits the original assumptions of invasion biology and offers us the growing evidence that they have not been confirmed by the science that tested them in the field. In a recent post, we reported that the assumptions that ecological “niches” are exclusive and therefore new species will displace former occupants, are not consistent with the fact that introduced species far outnumber the loss of native species. In fact, there is little evidence that introduced species have resulted in extinctions.
“Nature has no ‘Balance’ for us to keep”
Matt Ridley, in his weekly column “Mind & Matter” for the Wall Street Journal, invites us to revisit the concept of the “balance of nature” with the help of Ms. Marris’ book. Mr. Ridley is a British scientist who has written many popular books about human genetics and evolution.
In our interminable debate with native plant advocates, we find that the concept that nature achieves an equilibrium state that is, by definition, balanced, is central to their ideology. Their argument is that man has disrupted this balance and that he is therefore obligated to right this wrong. Furthermore, when this balance has been achieved, theoretically, nature sustains itself without further interference from man.
This is a powerful narrative with much intuitive appeal. Particularly for those who feel some guilt for the damage that man has inflicted on nature, the obligation to heal those wounds is strong. However, the scientific evidence is mounting that there is no such thing as a “balance” of nature, as Mr. Ridley tells us in his column:
“Academic ecologists have abandoned such a static way of thinking for something much more dynamic. For a start, they now appreciate that climate has always changed, and with it, ecology. Twenty thousand years ago the spot where I live [in the UK] was under a mile of ice. Then it was tundra, then birch forest, then pine forest, then elder, linden, elm and ash, then most recently oak, but beech was coming.”
Mr. Ridley goes on to lament that although science tells us that a stable balance in nature cannot be achieved, particularly at a time of rapidly changing climate, the notion still dominates practical conservation management, which he describes as: “preserve this rare species, maintain this habitat structure, freeze in time this ecological moment, return this degraded land to a particular state, whatever the weather and whatever the novel arrivals of exotic species.” These goals sound very familiar to those of us who follow the various “restoration” projects on our public lands in the San Francisco Bay Area.
We are grateful to Ms. Marris for bundling the recent science that dismantles the mistaken assumptions of invasion biology into a readable package that is being reported by the mainstream press. We anticipate that the public will eventually realize that the destructive native plant “restorations” in which the managers of our public lands are engaged are unnecessary and ultimately futile.
It’s just a matter of time!
“Emma Marris, Rambunctious Garden, Bloomsbury, 2011