Are We Just “Re-Arranging the Deck Chairs on the Titanic” aka the Planet?
A basic premise of the Native Plant Societies is that “native” plants are better than “exotics” for a variety of reasons, including benefits to wildlife. This is certainly partly or largely true, but may be irrelevant. The reason is that as a consequence of globalization, species have been widely spread and it is unrealistic to return more than a tiny fraction of the ecosystems to their native species configuration. Indeed humans themselves are one of the most invasive species and destroy the natural arrangement of habitats wherever they go. Unless the global human population reverses its current upward trend, there will be little left of anything resembling a natural environment in the not too distant future.
So what do we do? Give up or come up with a practical plan to maximize the potential of the remaining but somewhat homogenized ecosystems?
A. A DEFINITION: First you must realize that there is no single way to define native vs exotic species. This can be a hard pill to swallow but there is in fact a continuum between native and exotic species that depends on how far apart two species occur naturally and whether they are on the same continent. So it just depends on how the terms are defined and how confused the history of species becomes by naturalization and the mists of time.
B. DOES IT MATTER? There is something to be said on the positive side for non-invasive exotics IF they are beneficial for wildlife and can be controlled in a specific location. There is also something to be said for realizing that the proliferation of exotics/pests/diseases is so complete in many habitats and continuing to spread rapidly that returning to the natural communities is impossible. Let us be REALISTIC and PRACTICAL about what is happening. Demonization will not make invasive exotics go away. The establishment of global trade and travel long ago destroyed many barriers to immigration of exotic species.
So we are stuck with a large proportion of habitats as a mixture of native and exotic species with no practical way to separate them. Spraying herbicides to kill the so-called exotics can be very harmful and lead to an early successional state which results in a massive invasion of weeds. Allowing natural succession to occur may lead to disappearance of some exotic weeds without the damaging effects of chemicals. Often however exotics will proliferate and take over a site. It is impractical to spray a significant proportion of such damaged sites and attempt to recreate them by hand as pre-Columbian.
The general area of Boone where I live in the summer is currently undergoing massive invasion by many exotic species such as oriental bittersweet, mile a minute vine, and tree of heaven. There is really nothing that can stop them at a broad scale even using massive herbicide treatments. The forest habitat undergrowth is also being devastated by browsing of an over-population of deer. Without reduction of deer to a more natural level the native forests are doomed. Already the under-story consists almost entirely of toxic plants that deer will not eat (such as yellow buckeye, mountain holly, striped maple, spicebush, barberry, etc) and generally not the native tree saplings that would be the natural forests of the future. Surprisingly many people choose to ignore this massive loss of biodiversity and community structure and park agencies do not allow the hunting that would be necessary to reduce the deer herds.
There are many additional large scale environmental problems that are not easily if at all soluble- severe damage to soils and water by development, agriculture, industry, mining and logging and spraying of toxic chemicals. In the face of such discouraging problems we may choose to become the “masters of our tiny yard domain.” This enables us individually to attain a measure of control which is lacking in most of our lives and achieve some significant benefits for wildlife on a minute scale. This can result in a degree of self-satisfaction in our lives not attainable in many other ways.
C. A PLAN: I would prefer not to constantly praise the sole benefits of “natives” when they can be difficult to define, and sometimes impossible to physically separate from exotics without environmentally damaging methods. Certainly the goal should be to use natives first. I would prefer to debate the specific goals of gardening in each location and in nature at large and define the best approach using whatever beneficial native and non-invasive exotic species propagate well.
I suggest defining, evaluating and ranking the value to wildlife of plants over the growing season that most efficiently support specific types of animals- butterflies and birds especially- and consider their uses regardless of their place of origin. Following this approach over a 25 year period in our SW FL Manasota Key property has resulted in a fairly even split of 160 species between classical natives and exotics. However some species, such as the native strangler fig tree, are far more valuable than others. The ranking of beneficial species relies on the seasonally distributed uses of cover, nesting sites, consumption of leaves by larvae, consumption of nectar, consumption of fruit, and consumption of pollen. Achieving a proper temporal distribution of flowering/fruiting is crucial, especially during migration and reproduction. Some fruits are sugar bombs to be eaten immediately and others are more lipid rich and remain on the plant for months before being eaten. Just to give one example, mulberries are highly prized by birds in spring migration. The native species red mulberry is dioecious and does not produce enough fruit at the time of spring migration to be as beneficial as either the monoecious exotic black or white mulberries.
We owned a 107 acre wildlife farm near Galax, VA, for 15 years and have now completed our third summer gardening on 2 acres near Boone at 3400 feet. A somewhat similar split between natives and non-invasive exotics seems to work well for these VA/NC locations as well as FL. The early to late season phenology for the major nectar producing flowers (and for fruits later) in our Boone yard is roughly serviceberry, dogwood, ragwort, coral honeysuckle, daisies, azaleas, rhododendrons, hawk weed, fleabane, coreopsus, Japanese holly, beebalm, elderberry, coneflowers, Brazilian vervain, dianthus, cat mint, red hot poker, zinnias, milkweed, butterflybush, cup plant, goldenrod, Joe Pye weed, althea, great lobelia, asters. Since very few plants bloom for more than a few weeks (one reason the long blooming butterflybush and althea are so valuable in the mountains where they are not very invasive) it is crucial to have a sequence of blooms.
The photos illustrate just a few of the nectivores that come to exotic crocosmia (hummingbird- is it worse to plant an African nectar producing flower or put sugar water in a feeder?), exotic butterflybush (red spotted purple butterfly), quasi-native coneflower (great spangled fritillary), and native Joe Pye weed (red admiral).
D. A SUMMARY: Everyone should be the lord and master of their personal garden plan, but the minimum requirement should be that the plan benefits wildlife, and does no harm to the soil, and ground and surface water runoff. Try some non-invasive “exotics” that have a special benefit for butterflies and birds and use them to produce extra leaves, flowers and fruits which are not otherwise provided by “natives.”