Sunday, February 1, 2015

A Native Tree Is Not Just A Tree

It’s an ecosystem. It is more than just a collection of leaves, flowers and fruit. It is more than just a giver of shade and large limbs for swings. It is a home and giver of life to more than we even know.

Years ago we all learned that trees are an important source of oxygen. They take in carbon dioxide that we breathe out and give us oxygen in return. They also help clean pollution from the air. Learning this was like learning about magic. What an easy thing to do! We were all excited about planting trees to improve the Earth.

People went about happily choosing and planting trees. They planted them in their yards and in their schools. City parks and median strips were strewn with these oxygen machines. It was a glorious time. Nurserymen found exciting new choices to offer their customers - exotic plants from around the world. In my childhood city, crepe myrtles were all the rage and the city planted them everywhere.

New oak leaves ready to support insects
A few people knew that not all choices were equal. You see these places where we were planting our new trees were once home to forests of indigenous trees. Oaks, maples, hickories, and chestnut once ruled the land. Their foliage and flowers were the food and sustenance for thousands of native insects.

Native plants evolved with the native insects and scientists find more evidence every year that those insects largely can’t live on non-native plants. Now you might think that fewer insects is a good thing … until I remind you that butterflies are those insects. Remember the monarch butterfly that eats only milkweed (Asclepias) plants? When milkweed goes away so do those beautiful butterflies. 

Bird food!

Every plant species has an insect or two - or even 534 of them – that depends on them.

The mighty oaks that once lived here in vast tracts support 534 different species of moths and butterflies … that we know about. There may be more. 

Birds are very fond of those insects. Many birds eat insects as part of their diet. Many more feed them to their babies. I read a great article recently about research on a common backyard bird and its relationship to suburban/urban landscapes. From the article:

Contrary to what many people believe, “birds do not reproduce on berries and seeds,” Tallamy says. “Ninety-six percent of terrestrial birds rear their young on insects.” Because native insects did not evolve with nonnative plants, most lack the ability to overcome the plants’ chemical defenses and cannot eat them.

When we're choosing our trees, most of our trees, we need to consider not just our desires but the needs of the rest of our local world. We can choose trees that feed the local insects who in turn feed the local birds. The tree's fruit (or nuts) might also feed local mammals, and of course everything might become prey for the next member of the food chain.

It's a choice that we can all make, right in our yards and in community projects, and it has an immediate positive benefit. From the moment you plant it, the benefits begin for the insects.

By the way, I am glad to hear that my childhood city is changing. I read recently that the city is gradually replacing those crepe myrtles with other species, such as maple, dogwood, crabapple or sweet bay, in an effort to diversify its tree selection. The reasoning given was to reduce disease potential as well to incorporate more native species.

We all can learn again not just that trees are important but their importance is MORE than just oxygen and shade. Their role in the insect world is every bit as important. Arbor Day is coming up this month in Georgia; this year think about planting a native tree.  

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