- Become skilled in distinguishing between some native and non-native species.
- Survey their area for the presence of indigenous and exotic species.
- Examine interrelationships among living things.
- Assess the positive and negative impacts of alien species on native wildlife and habitat.
- Map the major features of their schoolyard or another survey site.
Students research the presence of native and non-native species in their area, the effects of exotics on local wildlife and habitat, interrelationships among plants and animals, and other observations relating to alien species. Students share their findings with the rest of the class and participate in a discussion.
writing materials, including pencils, observation sheets, and graph paper for mapping; clipboards; field guides to North American species
There's a battle going on and it's happening right in your neighbourhood. Alien life forms are waging war with native species to control habitat (including food, water, shelter, and space) and to fill the niches they occupy. Every organism has its own niche - the perfect arrangement of habitat in which it may flourish. The arrival of aliens means that native species face more competition for habitat. Newcomers have fewer diseases and enemies to deal with here than they would back home, giving them a decidedly unfair advantage. If an exotic species thrives, a pre-existing animal or plant will dwindle in numbers and possibly lose its niche. Interrelationships among the remaining species will never be quite the same. The balance of nature will be upset, and the biodiversity that holds together the web of life will be undermined.
A good illustration of this kind of imbalance is the rusty crayfish, a heavily clawed, aggressive crustacean imported from the southeastern United States as fishing bait. This cantankerous crawdad displaces native crayfish, forcing them out of their habitats and leaving them vulnerable to predators. It also feeds greedily on native aquatic plants, reducing their abundance and diversity and depriving invertebrates and young fish of shelter. European frog-bit, purple loosestrife, red-eared sliders, and zebra mussels are a few more examples of alien invaders that muscle out native species and throw ecosystems off balance.
- Based on the background text above and "Aliens Among Us", review with your class the major impacts of invasive species on native wildlife and habitat.
- Tell the students they are going to research the presence of some native and non-native species in their area and possibly extend their survey to their schoolyard or another site. They will gather data on habitat elements, including food, water, shelter, and space, plus interrelationships among indigenous and exotic species.
- The students should start by learning to identify some of the native and non-native species in their area. Among the resources they will need are field guides to birds, mammals, reptiles, amphibians, crustaceans, molluscs, fish, and plants.
- If you cannot take your students outdoors or do not have access to a suitable site, have them work in pairs or small groups and take a "virtual field trip" based on past observations and available data on species and spaces in your area.
- If a field trip is feasible, ask the students for suggestions on a survey site - preferably a wetland, meadow, forest, seashore, or other natural area. A park or your schoolyard will also do fine.
- Prior to the real or virtual field trip, prepare an observation sheet that will help students inventory a few examples of the following items:
- Native species: What indigenous animals and plants are present? Are there any rare or endangered species?
- Alien species: What invasive or naturalized life forms are present? Where are they located and how much space do they occupy?
- Interrelationships: Is there evidence of interaction among species? Are there signs of predation or competition between native and non-native life forms?
- Positive impacts: How do alien species appear to be benefiting other animals and plants? For example, are pollinating insects drawn to purple loosestrife and flowering-rush?
- Negative impacts: What harmful effects can be attributed to exotic life forms? Look for signs of monocultures (plant communities dominated by a single species) and native animals and plants that are crowded out of their homes.
- Habitat elements: Are there natural food sources, like fruits, seeds, and nectar? Is there a river, marsh or other source of water? Can wildlife find shelter in places like rock piles, thickets, tree hollows, and submerged logs? Is there space to grow and multiply?
- Each student can research a single alien species observed in your region in depth and write a short paper on its origins, how it got here, when it arrived, and how it helps or harms native wildlife and habitat.
- Have your students participate in an ongoing biological survey of exotic species or start their own monitoring study to track the presence and spread of alien invaders in your community.
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