Ecological principles & land cover characteristics

...Used to identify regionally significant natural resource areas (terrestrial and wetland)

Land cover characteristics and native plant communities

The following 6 attributes, based on the major ecological principles listed below, were used to identify Regionally Significant Terrestrial and Wetland Areas.

  1. Natural land cover
    • Less than 4% imperviousness
    • No maintained vegetation (agricultural or short grass)
  2. Size of the natural area
  3. Shape of the natural area
  4. Adjacent land cover/use
  5. Connectivity to other natural areas
  6. All native plant communities mapped by the Minnesota County Biological Survey that have not been destroyed since the survey was completed were identified as regionally significant regardless of size, shape and adjacent land use.

Ecological principles

1. The size and shape of an area is important

Some human activities, such as development and agriculture, eliminate and break up (fragment) native vegetation. When vegetation is broken up in numerous small and irregular shaped pieces (patches), the plants and animals found on the site, and the interactions that take place between plants and animals (e.g. predator and prey relationships) change.

  • The larger a natural area the more likely it will support populations of native plants and animals. A population is a group of individuals of the same species that is capable of reproducing.
  • Fragmentation of vegetation often results in a reduction in the nest success (number of offspring that survive) of some bird species. Small, irregular shaped areas have a greater proportion of edge area than interior area. More birds may be forced to nest in the edges. Nests of some bird species in forest edges may have a greater risk of losing offspring to predators (crows, grackles, brown-headed cowbirds). This is referred to as edge effect, the response of plants and animals to environmental conditions created by the edge. (Forest and grassland ground nesters are particularly vulnerable to predation.)
  • Edges do provide important habitat for many plants and animals and often have a high number of species. This is in part because fragmentation of vegetation often increases the occurrence of invasive, non-native (exotic) plants and animals that inhabit edge habitats. Over time, invasive non-natives often out-compete native species, leading to less overall species diversity at the landscape scale. What is of concern is the ratio of edge habitat to interior habitat on the landscape. Edge habitat and edge species (plants and animals) are often over-represented in fragmented landscapes.

2. Adjacent land use affects natural areas.

The introduction of non-native plant species into forest and grasslands from urban gardens, trampling of vegetation from heavy pedestrian or recreational use, and increased salinity of wetlands from road salts are a few ways that adjacent urban and agricultural land uses adversely impacts natural areas.

Urban and agricultural land uses introduce new predators and may increase predator populations. Wildlife impacts include increased mortality from cat predation, car kills, killing of wildlife (snakes and bats) by landowners due to misperceptions/fear, and reduced reproductive success if breeding is disrupted by human activities.

3. The connectivity of vegetation is important

The addition of impervious surfaces such as roads and buildings often fragments landscapes. Fragmentation and increased imperviousness change how plants, animals, wind and water move across the landscape.

Habitat connectivity may allow an animal to relocate when habitat is lost or degraded due to natural or human disturbance. Movement allows individuals from different populations to breed, which maintains genetic diversity in the population. Some animals have different vegetation requirements during different stages of their life cycle. For example, Blanding’s turtles require large wetland complexes for over wintering and dry, sandy soil grasslands for breeding. An animal’s risk of being killed (increased predation, road strikes) during movement increases in fragmented landscapes. Lake, stream and wetland habitat quality is dependent on maintaining vegetated riparian and lakeshore zones, and connectivity to upland vegetation.

4. Species diversity is important

Recent ecological research shows that a plot of land with many plant species is more productive and resistant to drought, pests, and other stresses than a comparable plot with only a few species.

Many human activities cause changes in the environment that lead to lower species diversity. Examples include excess nitrogen from pollutants, the introduction of invasive non-native species, and the disruption of natural processes such as natural water flow. These disruptions often lead to the elimination of many native species and the promotion of just a few species. These disturbed areas then are less able to tolerate outbreaks of pests and diseases and large-scale changes such as climate change.

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