False-rue anemone COSEWIC assessment and status report: chapter 8
Limiting Factors and Threats
In Canada, several subpopulations of Enemion biternatum are impacted by soil compaction and trampling, due to their proximity to public areas and trails. Loss of habitat due to invasion of tall grasses, wood cutting operations, soil erosion, and agricultural activities also pose threats to other Canadian populations of the Enemion biternatum. Spraying of herbicides and pesticides also occurs to the detriment of these plants. Road salting may be a limiting factor for at least one Canadian occurrence of Enemion biternatum (Austen, 1990).
Some populations of Enemion biternatum were found growing in conditions considered to be atypical for the species; adjacent to windfalls and tree cuts, edge habitats, within large growths of the exotics Alliaria petiolata or Aegopodium podagraria, amongst tall grasses, and along well-used footpaths. It is assumed that plant populations in these areas are on the decline; however, research is necessary to determine how seedling growth, seed output and germination in these populations differ from populations growing in more typical habitats (Austen, 1990).
The majority of landowners are unaware of the presence of Enemion biternatum on their land, or its rarity. The Upper Thames River Conservation Authority is aware of populations growing on their property through the work of J. Bowles.
The abundance of the exotic horticultural plant Aegopodium podagraria poses a strong threat to the Enemion biternatum population in the floodplain area of the Thames River, University of Western Ontario.
Populations 1 and 2 are threatened by their proximity to public areas and trails. In these areas, plant subpopulations may be threatened by soil compacting and trampling by foot, bicycle and/or ATV. These two populations are also threatened by encroachment of Aegopodium podagraria and tall grasses, respectively. Enemion biternatum plants in subpopulation 1h are already growing in a long narrow strip, in contrast to their normal growth pattern of large clumps.
Subpopulations 1g and 4 may be threatened by wood cutting operations or tree falls found in the immediate vicinity of the plants. Population 2g is susceptible to soil erosion. In addition, subpopulations 1c, 1d and 1h are close to the edge of fields where the potential for mowing damage to plants is relatively high. Herbicides or insecticides sprayed on crops in the spring could harm plants in the area. Subpopulation 1c is also threatened by garlic mustard (Alliaria petiolata) encroachment. Road salting may affect subpopulation 1e, which is down-slope from the road in a low-lying area. Thompson also observed a small group of people camping in the immediate vicinity of subpopulation 1e. Because this is one of the largest subpopulations of Enemion biternatum found in Ontario, camping here should be discouraged.
Certain subpopulations (2a and 2j) are limited to small clumps consisting of very few plants therefore these populations are at a higher risk of elimination due to their low population sizes.
The limiting factors presented above are based on details provided by Austen (1990). Development in the region of the floodplain habitats has only an indirect bearing on the species. The floodplain itself is a regulated habitat but the increase in population and development surrounding the habitat likely has resulted in an increase in trail use and substrate compaction as well as general disturbance that could promote expansion of alien species.
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