Wednesday, April 28, 2010

Native species

I’ve always been in favor of native species. It just feels like a good idea. The nonnative Japanese beetles that were brought into the country to sell to home gardeners as lady bugs have become a real problem – at least in my house where they drown in vases and die on the windowsills by the hundreds. The buckthorn in our woods is another example. For the first twenty years we lived here, I searched in vain for spring wild flowers in the woods. The only blossoms were the ones my mother and I had planted, rue anemone, nodding trillium, hepatica. The buckthorn had completely taken over the under story. When our girls Amber and Laurel were old enough to need summer jobs, I hired them to kill buckthorn. They pulled, cut and poisoned buckthorn. Now we can see through the parts of the woods where they and their friends worked. Best of all, the plants my mother and I set are spreading, and I’m finding new flowers, plants that must have struggled or lain dormant for decades. Three cheers for nonnative species control. Dave and I are planning on converting our least productive (and weediest) hay field to prairie this summer and, of course, planting native species of prairie grass and flowers.

In general, we aren’t really very good at planting native species. I have purple coneflower in my sun garden and Virginia bluebells in the woods along with the other woodland flowers that my mother helped me plant. Beyond that, our farm is a fine example of native and nonnative diversity. Our lawn (I can call it that because it is the relatively flat area that stretches from the back deck to the woods and the fields) is a wonderful profusion of flowers right now – violets, perriwinkle, forget-me-not, and ground ivy. The lawn is beautiful. There are so many flowers that I don’t even watch my step when I walk, I know the flowers will survive. But the grass itself looks terrible. The ground ivy is a vicious nonnative, taking over lawns, gardens, forests. My shade gardens are carpeted in ground ivy, and although I love its little blue flowers in May, I hate the way it chokes out the other flowers the rest of the summer. I’ve even lost a mugo pine tree to ground ivy – it was completely covered!

Then I read an article in the Macalester Today magazine about Mark Davis, the first biology professor I had at Macalester College over forty years ago. Davis believes that exotic species are here to stay and that we should learn to love them. He says that exotic species act a lot like native species and that local ecosystems now have about 20% more plant species in them than they once did because of the foreign species. He feels we should only try to control those nonnatives that are threats to human health (like avian flu) and to the economy (like gypsy moths and emerald ash borers). The article specifically mentioned buckthorn as a species that was already entrenched and not doing much damage.

I’ve walked the Mississippi River banks in late fall and seen all the green leaves of buckthorn (the last tree to hold it’s leaves) and grumbled about how it is taking over the world. Dave and I debate spraying herbicides on the ground ivy in the lawn; we’d lose the violets and the forget-me-nots. And the ground ivy replants itself faster than the other spring flowers. So I weed the shade gardens as much as possible and hope for the best, enjoying what flowers we get. And I curse the non-native species. Dave sprays surreptitiously and selectively, and vows to pull more buckthorn when he gets the time.

Evolutionary biologist Stephen Jay Gould argued that the movement of species around the globe should be viewed as a part of the evolutionary process, not necessarily a destructive force. Mark Davis advises that we learn to love nonnative species. One of my friends even suggested that the battle against ground ivy was un-winnable and I should just relax and enjoy the flowers. I’m keeping and open mind and working on my attitude.

1 comment:

  1. Well Joan, I admire your open mind. Keep it open! Difficult when it comes to nonnative species it seems.
    I am currently writing a book on this subject. Nwo I have done climate modelling and not biology. I have to say I am baffled by the scientific rigor of ecologists claiming that nonnative species are a threat. Almost all papers are riden by assumptions, very rarely by facts.
    Biggest problem for me is the fact that they use valueladen words over and over again to address nonnative species (aggresive, bad, weedy, outcompeting, killing, polluting, degrading, prolific). It is almost a copy of words used to descrive foreigners in some other era. You can never prove something is good or bad. What you could prove is that some effect is sgnificant or that an extinction is proven to be caused by a nonnative species. You won't find any of this in climate science. Climate scientist can voice their opinions of course. but not in scientific papers withut backup.
    What is even more disturbing is that when it is researched, the picture changes dramatically. In 2008, Sax and Gains researched every single documented extinction. The result: on continents, comeptition by alien species has never caused a single extinction. All 800 cases of extinction have been researched. It happens, rarely, on Islands.
    From all artciles, papers and casestudies I have read it becomes clear to me at least, that the attitude towards foreign species has much more to do with emotions. With indoctrination threw repetition and examples, which change our views towards plants and makes us categorise into native and nonnative.
    Nonnative species are scapegoats. Compare 60 extinctions worldwide by nonnative species to an estimated 13500-27000 extinctions caused by our species through hunting and habitaloss...Habitatloss by exotics in cultivation (potatoes, corn) and not exotics that have escaped into nature. We have an inborn anitpathy towards newcomers and towards change. That is clear. But it is not something to base laws on. Finally, I think people have great difficulty with accepting change, even if it is inevitable or a fact. The fact is that more and more species travell troughout the world, that the almost never cause problems and that this is not at all a nonnative only thing. Just ook up the Moutian pine beetle. Perfectly native, killing forests now totalling the size of New York State in Canada...Finally: nonnative species have proven to be valuable habitat/food for other species.
    I think if we say we have to control nature, this should be based on what a plant/animal has done. Not because of its origin. Just as with humans it seems the most sensible thing to do. Just like Mark Davis says.
    Sorry for the elngthy response and best regards!