“It is interesting to consider an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect…” (Charles Darwin, The Origin of Species [John Murray, 1859])
So begins the concluding paragraph of a rather reluctant revolutionary’s treatise on species variation and adaptation, sparked by his travels as a naturalist 25+ years earlier. Last week’s exploration of climate resilience planning put me in mind of Darwin’s multi-decade observations of the effects of various habitats and resources on life forms, so it seems a good place to jump into the deep waters of…
Ecosystems (an environment’s life forms ‘considered together with all the effective inorganic factors’ according to A. G. Tansley, seemingly the word’s first proponent), and just what makes makes an ecosystem resilient when changes and disruptions test the connections. In 1935, Tansley was writing about plants when he coined the term, but in the decades since the concept of ecosystems has been widened to social and business planning, with forays into economics, education, engineering, waste management, and (wouldn’t you know) the wide and sometimes weird world of technology.
Adding the word resilience brings us back to Darwin’s ‘entangled bank’ of life forms singing, flitting and crawling about — because variation, adaptation, and a certain level of redundancy of functions and effects of the various elements reduces an ecosystem’s vulnerability to stress. In general, the more diversity the better, but for those of you who’d like to dig deeper into the subject, here’s a list of recent publications (courtesy of ScienceDirect), with short descriptions that should whet or sate your appetite. As winter storms and the usual array of emergencies march across the continent, you could also take a deep dive into Darwin’s musings on the mysteries and myths of mid-1800s understandings of biology and evolution…
Ideas and concepts have their time and place, of course — but I’d like to bring the consideration down to earth, and tell you a story of a piece of desert I’ve known for some time now. I’m sitting in a small house surrounded by fruit trees. They grew from random seeds that arrived in composted food scraps, or via birds, each seed rooting in soil that has developed through several decades of applied manure, fallen leaves and duff, raked into mulch beds in the developing orchard. There’s an automatic drip water system, which also fills a basin for birds and assorted desert life to sip from. A cardinal flits past, a curved-bill thrasher calls from a treetop, and a robin preens her feathers on a tree branch outside the window. This is an ecosystem, made more resilient as trees have grown to provide shelter for birds, humans, and various crawling insects, worms, and other small lives through storms and changing climate. The birds are singing.
In the time this ecosystem has developed, the surrounding desert has changed. Though still lush for a time if the monsoon rains come, the summers are hotter and winter rains less reliable. Habitat corridors are now fragmented, natural drainages being narrowed and bladed away. A multi-year drought has diminished the populations of various wildlife — deer, rabbits, packrats, mice, and their predators. There are many more people in the valley now, accompanied by deeper wells. Meanwhile, more powerful industrial pumps create zones of depression near heavily pumped areas. The local community well has been deepened by 100 feet, trying to keep up, but current state regulations will allow the aquifer to be drawn well below its new depth. As it becomes clear to social planners that humans have promised water to more users than the desert southwest’s rivers can provide, the aquifer underneath the valley is being eyed to replace water that has been drawn from the Colorado River to serve the growing city’s population. I tell this story as a reminder that, whether natural, technological, or social, all ecosystems are relationships of organisms with their physical surroundings, which are part of larger ecosystems.
One system’s resilience may be inadequate in the long term, if larger ecosystems falter around it. Good examples can be found by walking through a forest, noticing how changes in the canopy affect the understory of smaller trees, bushes, grasses — and if you get down to your knees to reflect, the “worms crawling through the damp earth.” Or you may find yourself eyeing the way your own life intersects with your family, friends, neighborhood, town, city, and the larger (natural and social) ecosystems surrounding us.
Among these relationships, I hope you’ll observe examples of adaptation to changes in the larger systems. This is an aspect of species resilience Charles Darwin attempted, with the observational and scientific knowledge available to him, to define in his concept of Natural Selection. Though adequately addressing the various controversies that Darwin’s words have engendered in the last 160+ years would take far longer than this post allows, I’ll finish with the concluding sentence of his contemplation of an entangled bank, “There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”
Up next, Migrate, Innovate? — On moving with the times. Until then, take care of yourself, and help some others along the way. - B.
Here is a U. S. Forest Service link to a more scientific analysis of how forests can be managed toward resilience to fires, invasive plants, insects, and drought.
A deeper look at urban development plans in the Sonoran Desert, and their effects on groundwater and aquifers.
Practical but also poetic, my favorite kind of writing. Happy to have discovered and subscribed to your newsletter.