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Categorized | Outdoors

Earth Aliens

Garlic mustard is one of the alien (non-native) plants in Michigan that disrupts habitat by replacing native wildflowers and killing native butterflies that try to feed on it. Photo from Michigan.org.

Earth aliens are killing or replacing native species by out competing them. Does it matter to our lives, economy, social, and environmental wellbeing? How do invading aliens impact us?

About seven percent of plants in North America were aliens from other continents by 1840. Presently, about 37 percent of plants in native habitats are aliens. Farm fields are planted with non-natives where aliens are critical to our health and survival. Many non-native yard plants please the eye but have negative effects on animals and native communities. It is a problem when aliens escape and invade native habitats. We need crops and farm fields but we also need healthy native habitats without aliens.

Garlic mustard is one species replacing native wildflowers and plants in forests. Organized groups pull the alien mustard on public and private land to help native species. The Mustard White and the West Virginia White are butterflies dependent on native mustards but are killed when they feed on the garlic mustard. They recognize chemicals in garlic mustard when they are searching plants to lay eggs and the chemicals trigger egg laying.

Their caterpillars die when feeding on the plant. Besides direct death by feeding, the alien plant replaces native plants. This happens with other plants and insects that have specific nature niche adaptations. Plants and animals evolve to co-exist. When alien plants cause plant species to disappear, associated insects disappear.

Plants evolve chemicals over time that prevent herbivores from feeding on them. It allows successful reproduction of their kind. The Mustard White and West Virginia White have been able to circumvent the native mustard’s chemical strategies, feed on them, and survive while other species cannot use the plant. When only a few species evolve to feed on a plant, the plant’s ability to reproduce and survive is improved. Such biodiversity adaptations allow species to survive and perform vital functions in ecosystems.

Most aliens from other continents are unable to survive and disappear shortly after invading in new habitat. Those that live often become economic or health hazards. For Native Americans, small pox that arrived with Europeans was deadly because they had not evolved defenses. Various fungi have caused devastation and starvation. The Irish potato famine that caused the death and economic collapse for Ireland is one example. Agricultural scientists work to protect crops from corn smut, fruit flies, and many threats to cultivated crops.

The scientists also work to protect native communities and species important to the forest industry. White Pine blister rust had environmental impact leading to economic loss and community social hardship. When native plant communities cannot sustain themselves, the human economy declines causing communities problems. The alien emerald ash borer caused billions in economic loss since it arrived and has killed countless native animals. Animals dependent on ash trees have declined. The Dutch Elm disease caused loss of trees and the DDT treatment caused severe environmental problems. Eagles and other species were pushed toward extinction and we are still working decades later at great expense to remedy the pesticide-caused problems.

Native plants enrich soil fertility, maintain mycorrhizal fungi essential for nutrient absorption, and maintain nutrient cycles important for human communities. The economic importance is critical. Our nations soils continue to decline with loss of species disrupted by aliens. We add fertilizers to replace lost nutrients but native species do it more efficiently. It is important to help native species survive to build soils, support native insects, birds, and mammals to maintain our country’s healthy economic, social, and environmental triple bottom line.

To protect your interests, protect native species that support healthy biodiversity in your yard. Prevent alien species from simplifying healthy habitats. Alien species kill native species and harm our economy and social structure by impairing environmental health. Nationally, prevent current efforts to eliminate environmental law protections. Locally, manage your yard in a manner that supports native species survival.

Natural history questions or topic suggestions can be directed to Ranger Steve (Mueller) at odybrook@chartermi.net – Ody Brook Nature Sanctuary, 13010 Northland Dr. Cedar Springs, MI 49319 or call 616-696-1753.

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