A section of land where Himalayan blackberry dominates and is out-competing native plants and trees.
Figure Credit: http://www.clarkpublicutilities.com/index.cfm/our-environment/stream-team/eradication/invasive-plants-in-our-watershed-himalayan-blackberry/
Figure Credit: http://www.clarkpublicutilities.com/index.cfm/our-environment/stream-team/eradication/invasive-plants-in-our-watershed-himalayan-blackberry/
“It just doesn’t like to stop. It’s very tenacious. And so we just have to be more tenacious, - Urban Forester for Seattle Parks, Mark Mead.
The Invasion Curve. As time passes, the amount of area infested by invasive species increases exponentially and later peaks. It is most effective to resolve this issue by detecting this issue in the fetal stages.
Figure Credit: http://conservationdistrict.org/how/report-weeds Himalayan Blackberry distribution throughout the United States. All have been introduced.
Figure Credit: http://plants.usda.gov/core/profile?symbol=RUAR9 Why is a Decrease in Species Diversity Bad?
We Lose our Native Plants Blackberries out-compete and may destroy native species and trees in particular: Native plants are important to us because they provide us many medicinal uses as well as nutrition for different animals. Having a high species richness allows for a rich array of different uses of plants. For example, in the Pacific Northwest, yarrow is a Native plant that can be used to maintain thyroid health. Native plants also are more efficient in absorbing water runoff from storms, which would help maintain Washington's water quality as well as decreasing flooding and erosion in the area (Hays, David L, Kern Ewing). We Lose our Native Trees Himalayan Blackberries also out-compete Native trees in the Pacific Northwest. As many of us know, trees are very efficient in producing oxygen, cleaning the soil, controlling noise pollution, preventing storm runoffs, storing carbon, and have many other valuable uses (Nix, Steve). |
Invasives Decrease Species Diversity
The disturbance hypothesis states that the more invasive species you have, the less species richness there will be and this is proven to be true in regards to the Himalayan blackberry that is becoming more conspicuous in the Pacific Northwest. The Himalayan Blackberry thrives well in the Pacific Northwest and out-compete native species. This is due to their structure, their high seed dispersal rate,and their defensive compounds. Invasive Structure Out-Competes Natives Himalayan blackberry have the ideal plant structure needed in order to optimize their nutrition intake. This in turn, increases their growth rate. The blackberry have one of the largest root systems and cane cross-sectional areas as well as the lowest cane tissue densities. Their ratios of leaf area to plant mass and of xylem area to leaf area is also at the most efficient amount (Caplan, JS, and JA Yeakley). This is an advantage to increasing their water storage, conductance, and nutrient absorption. Their root ball is the power source for the plant and it so strong, that it is able to resprout through tough material, such as tarp. Thus, each Himalayan blackberry will remain thriving unless the complete root ball is removed when attempting removal ("Why Did Blackberry Brambles Become Such a NW Problem?"). This invasive has the trait that allows it to maintain a high and fast rate of gas exchange during dry summers, increasing its productivity (Caplan, JS, and JA Yeakley). This structure as well as their height to shade the under-story from sunlight allows for the Himalayan blackberry to out-compete Native under-story plants as well as prevent the establishment of trees, such as Pacific Madrona, Douglas Fir, and Western White Pine. Invasive Seed Dispersal Rate Out-Competes Natives Seed dispersal is very efficient for them as their blackberries entice birds and other animals to consume their berries and the seeds are then dispersed in more areas through feces. Invasive Defensive Compounds Increase its Survival Rate Banana Slugs in the Pacific Northwest feed on Himalayan Blackberry. Studies were done in the leaves of these invasives to find that young leaves contain high concentrations of 2-heptanol. This compound, when leaves are exposed or are eaten, emit these volatile compounds that will cause banana slugs in particular to stop feeding on the Himalayan Blackberry (Wood, W.F.). This compound was also found in mature leaves of the blackberry. Invasives Help Other Invasives In addition to the Himalayan Blackberry being efficient to thrive in the Pacific Northwest, their berries are also a food source to invasive animals as well. For example, European Starlings and rats feed on these and they begin moving into this "invasive-suitable" habitat ("Himalayan Blackberry"). This creates an ecosystem that is very efficient for invasive species to thrive in and begins kicking out and overtaking the environment that was once the Native's. Without any action, we will be at a point of no control over the blackberries and we will see very few native species left in our ecosystem and a high amount of blackberries. |
Invasives Shift the Current Ecosystem
Invasive species shift the current ecosystem so that it is less suitable for Native species. This applies not only to our Native plants, but also to our Native animals.
Conservation groups who have worked in Seattle parks attempting to remove Himalayan Blackberries have reported finding Native birds, particularly chicks, trapped in the thickets of the blackberry. Dense thickets of Himalayan blackberry is an ideal environment for rats so these invasive species will move in as well as there will be a lack of its predators present in these areas. These impenetrable blackberries can also prevent larger wildlife the access to water and other resources.
The roots of the blackberry are so powerful that riverbanks may be eroded, destroying Native species habitat, making it more difficult for Pacific Northwest salmon to thrive. Naturally, native plants help absorb storm water runoff, but with the Himalayan blackberry outcompeting and establishing the Pacific Northwest as their territory, storm water runoff with increase and in turn, so will erosion, flooding, and lack of water quality (Hays, David L, and Kern Ewing).
These thriving invasives also cause problems for people who simply wish to enjoy the parks as the biodiversity of the various plants and trees begin to all look like invasive Himalayan Blackberry.
Conservation groups who have worked in Seattle parks attempting to remove Himalayan Blackberries have reported finding Native birds, particularly chicks, trapped in the thickets of the blackberry. Dense thickets of Himalayan blackberry is an ideal environment for rats so these invasive species will move in as well as there will be a lack of its predators present in these areas. These impenetrable blackberries can also prevent larger wildlife the access to water and other resources.
The roots of the blackberry are so powerful that riverbanks may be eroded, destroying Native species habitat, making it more difficult for Pacific Northwest salmon to thrive. Naturally, native plants help absorb storm water runoff, but with the Himalayan blackberry outcompeting and establishing the Pacific Northwest as their territory, storm water runoff with increase and in turn, so will erosion, flooding, and lack of water quality (Hays, David L, and Kern Ewing).
These thriving invasives also cause problems for people who simply wish to enjoy the parks as the biodiversity of the various plants and trees begin to all look like invasive Himalayan Blackberry.
Original figure: Flowchart of Himalayan Blackberry and its negative causal effects from its increasing growth. by Tracey Wong