SWAN LAKE PARK INVASIVE SPECIES
Natural areas such as Swan Lake Park provide shelter and food for wildlife, remove pollutants from air and water, produce oxygen through photosynthesis and provide valuable recreational and educational opportunities. Invasive species can threaten these important services.
Invasive species generally are non-native plant, animal or pest species that out compete native species for resources and dominate space. Invasive plants impact species diversity and species richness by competing heavily for resources such as light, moisture and soil nutrients that native plants require to establish and grow, ultimately, affecting the intricate linkages that make ecosystems strong and resilient.
Invasive plants that invade recreational areas often reduce the area’s attractive and enjoyable qualities. Invasive plants may reduce native plant biodiversity, affecting the number of songbirds in the area. Walking through dense vegetation can prove difficult. Seeds and other plant parts can hitch rides on hiking boots, clothing, and pets resulting in new infestations, potentially over great distances.
The following map illustrates the extent of the invasive plant species problem in Swan Lake Park as reported by local residents.
Five of the invasive plants found in Swan Lake Park are categorized in the Ontario Landowners Guide as the most “aggressive” invasive species that can potentially reproduce over long distances (Category 1) while two species are categorized as Category 2, meaning they are “highly” invasive but tend to dominate a local area and not spread as extensively.
INVASIVE PLANTS: CATEGORY 1
Aggressive invasive exotic species that can dominate a site to exclude all other species and remain dominant on the site indefinitely. These are a threat to natural areas wherever they occur because they can reproduce by means that allow them to move long distances. Many of these are displaced by birds, wind, water, or vegetative reproduction. These are top priority for control, but control may be difficult. Eradication may be the only option for long-term success.
1) Common Reed Grass (Phragmites australis)
Invasive Phragmites is an aggressive plant that spreads quickly and out-competes native species for water and nutrients. It releases toxins from its roots into the soil to hinder the growth of and kill surrounding plants.
2) Dog Strangling Vine (Cynanchum rossicum)
The name “Dog-strangling Vine” refers to two invasive plants that are look-alike members of the milkweed family – black swallowwort and pale swallowwort. The vine forms dense stands that crowd out native plants. Leaves and roots may be toxic to livestock. The vine threatens the monarch butterfly, a species at risk in Ontario. The butterflies lay their eggs on the plant, but the larvae are unable to complete their life cycle and do not survive.
3) Garlic Mustard (Alliaria petiolate)
Garlic mustard is an invasive herb native to Europe. it has a strong, distinctive smell similar to garlic. Since its arrival in North America it has escaped into the wild and is now one of Ontario’s most aggressive forest invaders. Garlic mustard can invade relatively undisturbed forests. It hinders other plants by interfering with the growth of fungi that bring nutrients to the roots of the plants. The plant threatens several of Ontario’s species at risk, including American ginseng, drooping trillium, false rue-anemone, hoary mountain mint, white wood aster, wild hyacinth and wood poppy.
4) Manitoba Maple (Acer negundo)
Also known as the Box-elder, this is our only native maple that has divided leaves. These maples only grow to about 20 m but they grow quite quickly. A protoxin present in the seeds has been identified as a major risk factor for, and possibly the cause of, a disease in horses. Ingesting Acer negundo seeds, or other parts of the plant, may therefore be toxic to humans, in large doses. Acer negundo is a severe allergen. Its pollination occurs from winter to spring, depending on latitude and elevation.
5) Tartarian Honeysuckle (Lonicera tartarica)
Rapidly invade areas, out-competing native plant species by forming dense patches. Affect light and nutrient availability to neighboring plants. Produce toxic chemicals that prevent other plants from growing in that area. Fruit does not offer migrating birds the nutrients needed for long flights compared to native plant species. The flowers attract pollinators causing native species to reduce the amount of seeds they produce.
INVASIVE PLANTS CATEGORY 2
Exotic species that are highly invasive but tend to only dominate certain niches or do not spread rapidly from major concentrations. Many of these spread vegetatively or by seeds that drop close to the parent plant. They may have been deliberately planted and persist in dense populations for long periods. Control where necessary and limit their spread to other areas.
6) Black Locust (Robinea psuedoacacia)
The branches of young black locust trees have five centimeter spines that grow all along the branches and can tear the skin and damage eyes of people and animals that wander too close. Being a legume, black locusts have nitrogen-fixing nodules which increase the nitrogen content in soils, altering the growing conditions for other species. Black locust leaves, stems, bark and seeds contain gastrointestinal neurotoxins. These can be fatal to humans and some animals (horses in particular).
7) Oriental Bittersweet (Celastrus orbiculatus)
Oriental bittersweet grows by twining around shrubs and trees. It can easily overrun native vegetation, forming nearly pure stands. It can strangle shrubs and small trees and weaken or even kill mature trees by girdling the trunk and smothering the crown.
OTHER INVASIVE PLANT SPECIES
8) Either Chinese Elm or Siberian Elm
- Chinese Elm (or Lacebark Elm) (Ulmus parvifolia)
Smooth bark becomes flaky and blotchy as it ages, exposing very distinctive, light-coloured mottling, hence the synonym “lacebark elm”.
- Siberian Elm (or Asian Elm and dwarf elm) (Ulmus pumila)
Sometimes mistaken for Chinese Elm.
As ages, the bark becomes deeply ridged and furrowed and possesses a very rough, greyish-black appearance.
INVASIVE INSECTS
1) Japanese Beetles (Popillia japonica)
Adult beetles skeletonize foliage. While adults do not damage turf, they do feed on foliage and fruit of about 300 species of plants. Larval feeding on the fibrous roots of grasses makes this stage a destructive pest for turf. Injured turf initially wilts and yellows during August and September. Eventually, dead patches of turf can be observed.
2) Yellow-headed Spruce Sawfly (Pikonema alaskensis (Rohwer)
Larvae emerge in early spring and begin feeding on the succulent needles. Larvae initially feed on the new needles, leaving only short brown stubs. Once the new growth is devoured, the larvae move back on the branch and feed on the older needles. By July, infested trees appear ragged and yellowish-brown especially near the tops. Heavily-infested trees may be completely stripped of foliage. Three to four consecutive years of moderate to heavy attacks can kill the tree.
INVASIVE FISH
Goldfish (Carassius auratus)
Goldfish are quite tolerant of poor water quality, including water with low levels of dissolved oxygen and may threaten some native species in degraded ecosystems. Goldfish eat snails, small insects and young fish, making this species a competitor with and predator of native fish. They stir up mud and other matter when they feed, which increases the cloudiness of the water and affects the growth of aquatic plants.
INVASIVE TURTLE
Red-eared Slider (Trachemys scripta elegans)
The red-eared slider is the most common non-native species of turtle found in Ontario. This species was introduced through the pet trade and is now found in every continent except Antarctica. It has a brown to black upper shell, yellow stripes on its limbs and head, and a distinctive red or orange band around the eyes. Native to the U.S., the red-eared slider is commonly sold in pet stores, but many people who buy one do not realize that it can reach a maximum size of 25 to 33 centimetres and live for more than 30 years in captivity. The Red-eared slider competes with native turtles for food and basking sites and can make native turtles sick and can occupy areas that are favourable nesting and over-wintering sites for native turtles.