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Treebeard's Stumper Answer
25 Apr 97

The untended fields around school are beginning to turn brown. What's striking is that these wild plants are almost all introduced species. They were brought here, intentionally or not, from somewhere else, and they took over, driving out the native flowers and grasses as they spread. Indignation is possible, but there's also a stumper here. The invaders didn't evolve in response to our unique natural resources like our native plants. So shouldn't the natives have the edge in any competition for living space? How can introduced species actually dominate the landscape?

Introduced weeds are the latest of many natural invasions. There were Redwood groves in our mountains during the last ice age, and remnants like Wild Huckleberry still grow in sheltered places on San Marcos Pass. A few miles away on the dry river flood plain, I've found Great Basin Sagebrush, a remnant of a drier time. Each plant persists in a place that suits it. Humans add to the mosaic by plowing the fields, allowing extensive grazing, and building roads and homes. Disturbed areas are a new habitat, and new species have come. Change has made our natural world what it is, and of course it will continue.

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