There’s no argument about it. In the woodlands, grasslands and wetlands of the eastern United States, invasive plant control is the most important habitat improvement practice. Specifically, we are talking about existing habitats. Let’s define habitat improvement.
Quite simply, habitat improvement is any practice that makes a habitat better. Practices include invasive plant control, controlling other competitive plants, planting trees or wildflowers, improving hydrology and many more. The end goal with most habitat improvement practices is to improve or restore plant and animal communities.
Most habitats could use some level of improvement. Habitats nearly everywhere have been and continue to be negatively impacted directly or indirectly by human activity. This is the primary reason we are constantly restoring, improving, installing and maintaining something somewhere. It’s also the primary reason that it takes so much work to do so.
Invasive plant control is so important, because no matter what other practices you might implement, invasive plants will dominate the habitat if not managed. Invasive plants cause problems in numerous ways, but for the subject of this article, we are focusing on habitat degradation.
This article will focus on three key ways invasive plants cause habitat degradation. As you read through this, you should notice that these usually affect each other.
1) Prevent Native Plant Growth
One of the most significant limiting factors to plant growth is the availability of sunlight. When you hear the terms outcompete, crowd out, overtop or suppress regarding plant growth, they most commonly refer to creating shade. There are other things that affect plant growth like water, which some argue is equally as important, nutrient availability or pests and diseases, but they are usually less significant than light availability.
In woodlands, there are only a few tree species that do well in low sunlight. Of these, only a couple will continue to grow to maturity in deep shade. Eastern hemlock comes to mind. We see a similar phenomenon with native grasses, sedges and wildflowers. Some can tolerate part-shade, but the vast majority need sunlight to mature and continue to be healthy.
The aggressive and prolific nature of many invasive plant species outcompete native plants and plant communities by creating deep shade situations. The little native plant germination that occurs is negated by those plants soon dying. In some situations, very aggressive invasive plants will grow to cover healthy plants, including trees, to cause eventual death. This helps to explain why invasive plant control is more important than simply planting more native plants. Rarely do native plants suppress invasive plant growth without a bit of human assistance.
2) Degrade Soil Quality
Quality soil usually means a couple of basic things. It has a certain amount of organic matter, is relatively stable and physical and nutritional characteristics are regularly replenished. A more complex but necessary characteristic is a healthy soil microbial community.
One of the most significant threats to soil quality is erosion. Invasive plants can sometimes dominate habitat to suppress the growth of soil stabilizing plants. They also change the diverse plant and soil invertebrate communities necessary to continue creating quality soil.
But shouldn’t invasive plants hold soil like other plants? Their roots function the same way, but more stable soil situations occur with a more diverse and layered plant community. Our most stable soils occur from the soil holding roots of different plant types, the organic matter replenished by diverse types of decomposing plant material and the soil organisms that contribute to these other processes.
3) Reduce the Quality of Wildlife Food and Shelter
Healthy wildlife communities require diverse sources of food and shelter. Food and shelter in healthy communities are supplied by diverse native plants. This gives vertebrate and invertebrate wildlife plenty of nutritional choices and plenty of places to live.
Invasive plants fruit and flower the same way native plants do. They do it in abundance. We can also observe wildlife using invasive plants for food and shelter. However, we know that they provide poorer food quality while also offering fewer choices. Invasive plants, left unmanaged, will replace the diverse, higher quality native plants necessary for healthy wildlife.
Let’s compare this situation to a human community. Imagine if a person with a regular diet of great tasting and quality proteins, fats and vegetables had to start eating only bread. That person’s health will suffer greatly. Now imagine if peoples’ homes started to disappear; not just in supply because of a growing population, but actually disappear. If this happens to a whole community, everyone suffers, and people will begin to move away. This scenario strongly parallels everyday situations with wildlife habitat.
Make it a Priority
Many homeowners and landowners engaged in habitat improvement often learn as they go. For that matter, even most conservation professionals learn on the ground management on the job. One of the most important lessons they learn and often the number one reason for project failure or habitat decline is the need for continued invasive plant management. Across the board, whether the project is a backyard habitat, woodland, grassland or wetland, put invasive plant control at the top of your list.