Dr. Douglas Tallamy, author of Bringing Nature Home: How Native Plants Sustain Wildlife in Our Gardens, was the keynote speaker at the Western Massachusetts Master Gardeners Spring Symposium last week. His talk focused on the need for more insects to make our gardens – and the world – healthier and more ecologically balanced. “A mere 1 % [of all insects] interact with humans in negative ways. The other 99 % pollinate plants, return the nutrients tied up in dead plants and animals to the soil, keep populations of insect herbivores in check, aerate and enrich the soil, and as I keep stressing, provide food either directly or indirectly for most other animals,” Tallamy writes in his book and illustrated in his talk.
His enlightening talk covered a lot of ground, but two ideas made a particular impression on me. The first was the idea of the environmental carrying capacity of our local landscape, and ultimately of the whole earth. The term carrying capacity refers to the amount of resources needed to sustain a certain population. It is easy to understand that a given population of insects, or birds or whatever, will decline when the food they require decreases.
So, what happens when, for example, the emerald ash borer, which is a threat inMassachusettsright now, were to kill all the ash trees? Forty-four insect species rely on the ash tree to survive. No ash trees; no more 44 insect species. And that means reduced food for the creatures who depend on those insects so their populations will decline as well. Insects are the very bottom of the food chain and we usually do not consider how important they are to the wildlife that we enjoy. At least, that is true for me.
Tallamy said many people ask him why insects can’t eat some other tree or plant? He explains that over thousands of years plants and insects have evolved together. The insects’ digestive systems have adapted/evolved to digest the particular chemicals in a plant’s foliage. They cannot immediately adapt to a new plant. That is one of the reasons that invasive plants can take over. The food web of insects, birds and wildlife cannot keep the invading plants in check.
The second idea Tallamy put forth is that not all native plants are equal. Some plants support many more species of wildlife than others. This was an eye opener for me. I have been talking about the benefits of native plants for a long time, but this idea never occurred to me. As you might expect, trees are the most productive in having what it takes to support many insects and birds. Trees are big. But even here, some trees are more productive than others. In his book, and on his website, www.bringingnaturehome.net, Tallamy lists the 22 of the best woody plants beginning with oaks that support 534 species, down to the chestnut which supports 125 species. Black cherries, maples and willows are also highly productive.
If we don’t have the room to plant an oak or two, we might be able to fit in a crabapple or some blueberries. We can plant asters, morning glories and lupines in our ornamental gardens. We can not only marvel at and admire the lupine meadows that some people in our area have cultivated, we can thank them for supporting 33 species of wildlife.
Those lupine meadows also remind up that birds and other pollinators need clumps of productive native plants. Their eyesight is not always good so they need big clumps of a useful plant to catch their attention. Tallamy pointed out that 80% of our food crops are pollinated by animals. It is clear that supporting that wildlife is very important in our area where there is a growing number of farms.
Lately I have been talking about the benefits of reducing the size of our lawns. Tallamy said that 92% of landscape-able land is lawn, lawn which is a monoculture that does not support wildlife. He suggested that if we reduced the amount of lawn in theUnited Statesby half we would have 20 million acres that could be put to native trees and other native plants. This would certainly increase the carrying capacity of our neighborhoods and our nation.
Suburban yards can play an enormous part in restoring the health of our ecosystem. A whole neighborhood that includes a substantial number of native trees, shrubs and other plants can make a significant impact.
I am so grateful to the Western Massachusetts Gardeners for bringing us this excellent program that included Ellen Sousa of Spencer and the author of The Green Garden, as well as workshops on making compost, hypertufa containers and bentwood trellises that not only make our gardens healthful and productive, but beautiful as well.
Their Spring Symposium is their big educational effort of the year, and there are two more Symposia coming up on April 6 in Holyokeand April 13 in Lenox. Check their website http://www.wmassmastergardeners.org/ for complete details. However, they hold soil testing events, phone and email hotlines where you can get your questions answered, and lots of question answers right on the website. They even have a speakers bureau that can send a speaker to your club, or class, or other organization. If this is of interest to you send an email to firstname.lastname@example.org for more information.
Now I am wondering how many of us will find a place to plant an oak. Or a crabapple.
Between the Rows - March 23, 2013