Frequently Asked Questions

Q: What is an invasive species?

A: Invasive species are those which establish a population, reproduce rapidly, and displace native species. An invasive species can be a native species that becomes locally aggressive, usually because of some human-caused habitat change, or an invasive species may be a non-native species.

Q: What is a native plant?

A: This depends on where you are. In the USA , we usually define native plants as those which have been present since the time of European contact.

Q: What is a non-native plant?

A: A non-native plant is a plant that is accidentally or intentionally distributed outside of its historic range by human activities. For example, a species from Europe and Asia planted as an ornamental in the USA is considered a non-native plant. Humans may transport USA species to regions outside of their native range, but which are still within the USA . For example, a California poppy growing in Alabama would be considered a non-native plant.

Q: What is a non-native, invasive plant species?

A: Non-native, invasive plants are those outside of their historic range, usually originating from human settings (gardens, aquaria, agricultural areas, water gardens, cultivated roadways, etc.), that continue to reproduce and displace native species reducing the biodiversity in natural areas. On their home turf, plant and animal populations are kept in check by natural controls. However, when a species is introduced, accidentally or intentionally, into a new landscape – one not adapted to its presence – the consequences can be devastating. “Invasive” plants and animals sometimes spread unchecked, disrupting natural cycles, crowding native species and costing billions in property damage and lost economic productivity. More than 4500 foreign species have gained a permanent foothold or taken root in the U.S. during the last century.

Q: Are all non-native species invasive?

A: No. In fact, many non-native species do not cause any problems at all in their new environment. But when non-native species ARE invasive, drastic and widespread changes in ecology and landscape occur.

Q: Why do some non-native species explode in population and become invasive?

A: Recall that the invaders are usually non-native species. Free from the herbivores and parasites which keep them in check in their native range, they reproduce rapidly. They increase their numbers, unfettered by natural controls, and may displace the native plants. When the populations of native plants are reduced, the animals that depend on them may perish. The functions of the entire ecosystem are disrupted. Invasive plant species are truly a form of biological pollution.

Q: What is a weed, and is it different from an invasive species?

A: For a gardener, a weed might be a misplaced plug of grass. For a corn farmer, a weed might be a clump of nightshade. By definition, a weed is any plant that interferes with human activities and is not valued where it is growing. For the Adirondack Park Invasive Plant Program, our weeds interfere with conservation activities because they displace our native Adirondack plant and animal communities and decrease the biodiversity of our natural areas. In this context a weed is the same as a non-native, invasive plant species.

Q: How do weeds (non-native, invasive plants) decrease biodiversity?

A: Thick growths of non-native weeds can displace the native plants that once provided food and shelter for native animals. As weed populations rise, native species populations may fall. The worst weeds can even change the character of the habitat by changing processes like nutrient cycling, flooding, and soil profile development. The worst weeds may alter natural ecosystem processes and impact or halt native species recruitment.

Q: Plants move around naturally…isn't the arrival of new plants a natural process?

A: It is true that plants do change their ranges, usually over periods of thousands of years. We are not concerned with these slow changes. The invasions we are worried about are the ones that humans have caused, and which result in an accelerated loss of native, Adirondack biodiversity. Human activities outside of, and within, the Adirondack Park have created superb niches for the success of invasive plant species. Expansion and importation of invasive plant species is generally human induced and not a natural ecological process.