In North America, non-native species of honeysuckle (Lonicera spp.) can quickly grow and spread into dense thickets, disrupting natural ecosystems. Although the plants provide cover for wildlife and food for insects and birds, these honeysuckles out-compete native plants for light, soil and water, eliminating the native plants that the wildlife depend upon naturally.
Short Term Benefits
The fast growth of honeysuckle bushes, in particular Japanese honeysuckle (Lonicera japonica) and Tatarian honeysuckle (Lonicera tatarica), can help prevent erosion on exposed soils, such as on banks and hillsides. The dense foliage, flowering and seeds may provide quick cover for animals for shelter, or provide leaf or nectar food to insects.
The fast growth of non-native honeysuckles quickly can decimate ecosystems. Abundant foliage and sprawling stems shade out ground-dwelling native wildflowers and grasses, many which have specific pollinators or have unique relationships intertwined with the needs of native insects, birds or animals. With honeysuckle foliage already shading out and diminishing the vigor of native plants, the honeysuckle has less competition for the moisture and nutrients in the soil, allowing it to further grow unimpeded. Although abundant flowers and then seeds can provide nourishment to some native insect and bird species, germination of the seeds perpetuates the spread of honeysuckle and its out-competition of native plants.
Alteration of Animal Populations
With honeysuckles invading North American landscapes, the physical presence of thicket branches can deter natural land migration of animals. For example, a native wildflower may produce seeds that are eaten by a specific bird species. This bird is a primary food source for a fox. The honeysuckle chokes out or fully eradicates the wildflower, and in turn reduces food available for the bird. Fewer birds survive, and thus the fox has fewer birds to prey upon.
Moreover, just because a honeysuckle provides beneficial leaf, flower nectar or seed food to an ecosystem does not mean all insect or animal species benefit. The presence of honeysuckle can give an unfair advantage to one species of butterfly, for example, since it favors the honeysuckle nectar. This unnatural disruption can cause one butterfly species to outnumber other native species, potentially further disrupting other animals that rely upon the butterfly as a source of food.
Disruption of Rejuvenation
In some ecosystems, such as woodland savannas or prairies, the infiltration of non-native honeysuckles can prevent rejuvenating wildfires from occurring. The dense foliage of the honeysuckles creates a soil that is barren of grasses and other dry fuel to feed the occasional natural wildfire. Native plant species that rely upon the fire to release nutrients into the soil or to crack open hard seed coats will be put at a disadvantage.
Other effects of the honeysuckle can inhibit ecosystem health, from preventing seed germination on shaded ground to altering snowcover depth, soil moisture or wind patterns. Within a larger ecosystem, these small, seemingly trivial changes can have drastic effects on other organisms nearby.
Changing of Biome
Initially, the introduction of honeysuckle seeds into a native North American ecosystem will not create drastic changes. As the honeysuckle bushes grow, spread and make fruits that are eaten and scattered by birds, greater implications can be seen in the biome, or habitat type. A forest with floor shaded by honeysuckle may find a lack of tree seedlings, and thus the forest slowly becomes thinner and more open and sunny over time. Or, a grassland soon has honeysuckle thickets that choke out grasses and prevent the natural occurrence of fires. Without fire, tree seedlings have a chance to germinate and reach adulthood, potentially modifying the prairie to an open forest setting.