Invasibility

[2] There are many factors, abiotic and biotic, that can raise or lower a habitat's invasibility, such as stress, disturbance, nutrient levels, climate, and pre-existing native species.

Typically invasive species favor areas that are nutrient-rich, have few environmental stresses, and high levels of disturbances.

[6] For example, the Asian shore crab (Hemigrapsus sanguineus) has almost identical abiotic niches in its native and invaded habitat[7] but the European Green Crab (Carcinus maenas) has the ability to adapt its abiotic niche as it can survive in a wide range of water temperatures and salinities.

For example, the invasion of cordgrass (Spartina anglica) in salt marshes was highly dependent on salinity and sediment type and no biotic factors.

[4] Propagule pressure is a composite measure of the number of individuals of a species released into a region to which they are not native.

[citation needed] Propagule pressure is the main reason why the density of some invasive species is higher near the site of introduction.

[8] It has been proposed that disturbances increase invasibility to the degree that they cause the natural habitat to deviate from its original state.

[4] For example, when nutrients were added to an aquatic plankton environment it resulted in increased bacteria growth which facilitated the invasion of ciliates since the competition for resources was decreased.

For example, large scale nutrient run-off in the New England area has caused the invasion of Phragmites australis an exotic vascular plant.

[11] Stresses that limit metabolism or resource acquisition - such as extreme temperature and toxins - has the ability to both increase or decrease invasibility; this is dependent on the invader's characteristics.

[8] If the invader has optimum performance at a resource level that only slightly overlaps with a native species than it will have a greater chance invasion.

[8] A habitat with high species diversity results in lower total resource availability thus decreasing the success of an invader.

[1] The most commonly invaded types of habitats include those that are man made, such as gardens, farmlands, urban landscapes, ecosystems with nutrient rich fertile soil, such as forestry plantations and forest clearings, or areas of high levels of disturbance, such as coastal and riparian habitats.

[1] These habitats include mountains, cliffs, bogs, dry grasslands and coniferous woodlands, deserts, and savannas.