Biodiversity: Native Plants and Beyond

Gardens have always embodied and reflected society’s values. Elaborately tiled Moorish gardens with their pools of still water; ornate Renaissance statues and tortured boxwood parterres; riotous Victorian annuals; Arts & Crafts borders ‘painted’ with perennials … every era has its own gardening style and attitude.

So, what about present-day gardens? How are people incorporating new ideas about native plants and gardening for wildlife? Well, it turns out that in just the past thirty years, attitudes seem to have shifted in some fascinating ways.

This conclusion is based on a bit of informal research that I performed recently. On the theory that the relevance of a topic, to the general public, is indicated by the number of times it appears in New York Times articles, I searched NYT archives to find “gardening for…” followed by these six terms: native plants, birds, wildlife, butterflies, pollinators and biodiversity. And I divided the query into three 10-year time spans, from 1981 until 2011. While this may not qualify as rigorous scientific inquiry, the results are intriguing nonetheless. Do you have any guesses about the results? Three significant points stand out, and lead to a fourth, potentially controversial, proposal.

1. Overall frequency

It probably comes as no surprise that the hierarchy of hits is the same as listed above: native plants first (1257 total hits) and biodiversity last (57). In between were birds (923), wildlife (362), butterflies (311) and pollinators (74).

Clearly, pollinators and biodiversity are the new kids on the block. Until 1991, pollinators were mentioned only six times (in articles that also mentioned gardening) and biodiversity didn’t show up at all.

The near tie between gardening for wildlife vs. for butterflies hides the fact that in the first ten years of the search, wildlife showed up almost twice as much as butterflies (86 vs. 47), but in the ten years just past, butterflies took a tiny lead over wildlife (128 vs. 124). So, apparently wildlife was much hotter then, and butterflies are slightly hotter now.

2. The influence of current events

We all know, in a vague sort of way, that historic and economic events can powerfully affect garden trends. My search results starkly confirm this fact. Between 1981 and 1991, all six of the topics, taken together, were mentioned 747 times. In the next ten years, from 1991 to 2001, they showed up 1311 times, an almost double increase that seems natural in hindsight, given how sensible these ideas appear to us now. In the eighties and nineties, times were pretty good, social norms relaxed a bit and the economy was strong, so (I’m theorizing) maybe gardeners were more open to new ideas, even ideas that cost a little extra to try.

Then came the 21st century: the trauma of 9/11, followed by the angst of economic collapse. From 2001 to 2011, the search totals dropped 35 percent, from 1311 to 926. For three of the six terms, the totals decreased first between 2001 and 2006, then again by an even greater amount between 2006 and 2011. Interestingly, though, mentions of wildlife, pollinators and biodiversity increased in the last five years.

3. Biodiversity enters the scene

I believe this recent shift may be due to what I somewhat jokingly call ‘The Tallamy Effect.’ Doug Tallamy’s book, Bringing Nature Home, was first published in 2007, and has been selling steadily ever since. As he so eloquently states in his website:

“Humans cannot live as the only species on this planet because it is other species that create the ecosystem services essential to us. Despite the disdain with which we have treated it in the past, biodiversity is not optional.” (italics mine)

In his book, he clearly explains that if we want to help the environment we must garden with native plants that provide food for insect herbivores (not just pollinators), which in turn support biodiversity and entire ecosystems. This compelling message seems to be reaching deep into the public’s awareness. The evidence?

Guess which of my search terms increased the most in the last five years. Yep. Biodiversity: up by a whopping 150 percent, followed by pollinators and wildlife (up 80 and 40 percent). As a society, our awareness seems to be moving from appreciating large, obvious things – plants, birds, butterflies – to recognizing the importance of increasingly less obvious things – wildlife, pollinators and now, just a concept: biodiversity.

Beyond the data: a radical proposal?

I am grateful to Doug Tallamy for helping us see the vital link between our gardening choices and the biodiversity upon which life depends. He writes:

“What will it take to give our local animals what they need to survive and reproduce on our properties? NATIVE PLANTS, and lots of them.”

I agree wholeheartedly, and many others do too.

However, if we think of biodiversity only in terms of species – plants, insects, birds, mammals, etc. – we are missing an important piece of understanding.

Biodiversity is the collection of all the ecosystems, species and genes in a region. Research has proved beyond doubt that species diversity makes an ecosystem more resilient and able to adjust to change. Similarly, ecosystem diversity makes a region better able to recover from disturbance. And, in the face of change, genetic diversity helps individuals produce – via sexual reproduction and the mixing of genetic material – further generations of individuals who will be variously more or less able to survive new conditions and, when things work out well, to procreate further. This is the essence of natural selection.

When we garden with plants that have been propagated vegetatively (and are therefore genetically identical), or hybridized to maximize whatever aesthetic quality happens to be in fashion, we are circumventing natural selection. In fact, what we’re doing is called artificial selection, and I’m not sure humans should be trusted with such a big responsibility. Of course we need artificial selection for agriculture (as that industry is currently practiced), but do we really need it for flowers??

Worse than that, though, we are contributing to genetic erosion. This is the shrinking of a species gene pool, which results from extended inbreeding and/or the complete absence of sexual reproduction. (Many plants do self-pollinate, but that’s never their only reproductive strategy.) The consequences of genetic erosion include a constricting of evolution and an increased vulnerability to epidemic disease.

So, while we native plant gardeners work to increase species diversity, could we also direct our attention to its essentially invisible cousin, genetic diversity? I believe we should, and one way to start would be to re-evaluate horticultural breeding practices.

Could we require breeders to produce plants primarily from seed? Unlikely, given the nature (and advertising power) of the horticulture industry and our own human attachments. Could we ask nurseries to propagate more plants from seed? Well…we can try. We’re already asking them to sell more natives, and that seems to be working pretty well. And while we’re at it, let’s request that seed be collected from sexually reproducing parent plants, with no horticultural interference.

Long shot? Yes. But five years ago, who would have predicted that we would ever see fundamental change in the great American lawn?  Long shots do sometimes succeed.

After all…those complex chemical defenses that Doug Tallamy discusses in his book, those molecular concoctions in plants’ foliage to which tiny insects must adapt: how do they come into being? They develop via the elegant and oh so gradual process of co-evolution with other organisms, made possible by that crucial and often overlooked kind of biodiversity: genetic diversity.

So here’s a thought: let’s stop overlooking it. With climate change fast approaching, the plant kingdom is going to need a full gene pool and the freedom to use it.

© 2011, Sue Reed. All rights reserved. This article is the property of Native Plants and Wildlife Gardens. If you are reading this at another site, please report that to us