Susan Handjian is a garden educator in the San Francisco Bay Area. She was a contributing editor of Plants and Landscapes for Summer-Dry Climates.
By: gardencoach, 8:54 PM GMT on November 30, 2012
The one process now going on that will take millions of years to correct is the loss of genetic and species diversity by the destruction of natural habitats. This is the folly our descendants are least likely to forgive us.
- E. O. Wilson
Hardly a day goes by that we don’t hear or read about biodiversity. First, what does the term mean? It is a shorthand combination of two words - biological diversity that describes the variety of life on earth. It includes genes, species, populations and ecosystems in the soil, on top of the soil, in the water and air. In other words, it’s the sum total of non-human species with which we share our planet. Maintaining biodiversity is, to the minds of most scientists, the key to meaningful human survival. The more variety there is the better off we are.
It is such a large-scale concept, with far-ranging consequences, that it’s difficult to think of it in terms of one’s own garden. There is a strong connection, however, and although the home gardener may not be able to halt over-development and loss of habitat, natural gardening practices can stave off potentially disastrous effects. Understanding biodiversity also helps us to grasp concepts like ecology and sustainability.
Here’s the crux of the problem: The wealth of organisms on earth is staggering, but at the same moment these organisms benefit man by providing something called ecosystem services, species and systems are being damaged and degraded, some disappearing, by the hand of man. As biodiversity declines, we jeopardize our own survival as a species. Extinction is irreversible, permanent.
Human settlement of lands, both gradual and abrupt, has permanently altered the millions of species with which we share the planet. We reside at the top rung of species. Has our singular ability to name and catalog the remainder of species caused us to believe that we are not part of a whole, not one with the rest of life on earth? If that is the case, we have to seriously reconsider our views before it’s too late. Whatever our politics, it's abudantly clear that our own survival depends on the survival of as many of our companion species as possible.
What specifically does biodiversity do for us? Taken together, earth’s undisturbed ecosystems, forests, grasslands, wetlands, streams, estuaries, and oceans, provide materials, conditions, and processes that sustain all living things on earth. These are called ecosystem services.
A most wonderful book entitled Sustaining Life: How Human Health Depends on Biodiversity (Eric Chivian and Aaron Bernstein, eds., Oxford University Press, 2008), contains the best explanation and discussion of ecosystem services I’ve ever read, and I refer to their terms, below.
The vastness of these benefits can be almost overwhelming, but listing them is helpful because it allows us to see how they affect our every moment on earth.
Provisioning Services – Products obtained from ecosystems
Regulating Services – Benefits obtained from environmental regulation of ecosystem processes
Cultural Services – Nonmaterial benefits obtained from ecosystems
A sense of place
Supporting Services – Services necessary for the production of all other ecosystem services
Primary productivity – production of energy through photosynthesis
Nutrient cycling – the movement of essential elements throughout the environment
Pollination – the partnership of plants and animals that help plants reproduce
Take a good, close look at the final three categories. Considered together, they are the engine of all other ecosystem services. Net primary production (NPP) is the amount of plant material generated during a year through the process of photosynthesis. It provides the energy that powers all ecological process and thus allows for the provision of all other ecosystem services.
So, what about the garden and the gardener? Where do we fit into this?
If Biodiversity has an antonym, it is monoculture. Think of the lawn dominated landscapes so common to neighborhoods grand and modest. A lawn, a hedge of non-blooming plants, a row of roses – they’re all that’s needed to say the house has a landscape. The gardeners come by periodically to mow the lawn, trim and shear, apply fertilizer and pesticides. As a result, there are few if any insects and no birds. It’s a deliberate wasteland, inhospitable to most organisms, the exact opposite of what we as stewards and caretakers of the planet must be providing for our non-human companions.
Isn’t it amazing to realize that these supporting services describe what goes on in a healthy, natural garden?
For the gardener, the best protection and encouragement of biodiversity I can think of is a home garden that is densely and exuberantly filled with a great variety of plants, with physical connections between plants and several vertical levels. The health of soil is protected and encouraged. Pesticides are not used in this garden, and as a result there is a huge variety of insect life. If these many species of plants flower, they do so at different times of the year so something is always in bloom. Because flowers are allowed to go to seed and seed heads remain on plants, the air is full of a variety of birds, some seed eaters, and some insect eaters. Water is available for wildlife, as is natural cover in the form of both living and dead plants. A tree branch in a brush pile, for example, provides shelter and food for a vast array of decomposers, species we don’t particularly want to look at but that nevertheless provide a service whose value can’t be overestimated. A toxic-free environment with an emphasis on recycling and resource conservation is an investment in planetary health.
Enrichment and support of the innate connection of humans to their environment will only result in a healthier life for us all.