Buddleyas (Fall 2005) · 1177 days ago by Julie Loyd
Nine of us sprawled in a gloomy little room hung over the water at the Shaw Ferry Landing. Drying salt water from our morning eelgrass collecting left little white rinds on our pants, and we ate Cheezits and Oreos so singlemindedly that crumbs sprayed.
Jennifer Leach spoke to us about her graduate studies as a wetlands restoration biologist. She was a commercial photographer for several years in New York and Alaska, but after a decade of that went back to school. She studied in the UW forestry program as an undergraduate and is now working on wetland restoration as a graduate student.
She was with us to collect eelgrass seed as part of the Bellingham Bay restoration project, but spoke to us about her research on the Toulte River near Carnation. Sandy Wyllie-Echeverria also commented.
Wetlands are directly important to humans because they help to control flooding. Water passing through a wetlands is cleaned. Indirectly, they are part of the interconnected ecology of species. Migrating birds, for example, often stop over in wetlands. Some species entirely depend on wetlands. We take an esthetic and philosophical joy in a nice wetland. It is likely that there are other benefits to wetlands that we don’t yet know.
Current national policy on wetlands is no net loss. In Washington State, developers must follow four steps:
Can they avoid developing in a wetland?
If they can’t avoid it, can they minimize their impact?
If they must impact a wetlands, they must mitigate the impact by transplanting the wetlands somewhere else, or by restoring another wetlands. So, the abandoned industrial land thats being restored in Bellingham is in exhange for acerage that will be taken out of the ecosystem.
Legislation on monitoring keeps changing. Now in WA coastal areas, a project has to be monitored for five years. Because ecological systems take time to reach their final stage, five years is probably far too short.
A lot of restorations are failing. For one thing, monitoring requirements are often not enforced. Long-term planning is often not factored in. And finally, we often don’t know enough to establish a successful ecosystem.
For example, there was a tidal marsh restoration project in California. Spartina foliosa is a cordgrass that serves as a habitat for the 200 Light-footed Clapper Rails in California. These birds pin their nests to the spartina, and as the tide rises and falls, the nests do too. A major cause of the birds failure to thrive is when the nests drown. Although people managed to get Spartina to grow in the new site, Clapper Rails didn’t nest there. It turns out that a herbivorous and a carnivorous insect live on Spartina leaves. There weren’t enough carnivores to keep the herbivores from shortening the leaves.
One threat to ecosystems is invasive species. Every area has a limited amount of space, water, nutrients, and other resources. In a mature ecosystem, species have evolved to keep each other in check. When there’s been a major disturbance: a glacial retreat, a volcano, a fire, a clearcut, then pioneer species such as fireweed colonize the empty space. Nowadays, these are often invasive species from somewhere else: nettles, thistles, plantago, scotch broom. Pioneer species are able to colonize areas first because their seeds are dispersed by wind or water, and they are able to thrive with fewer nutrients or less water.
Since there are only 60 rooted vascular plant species in marine environments, succession is often a relationship between plants and animals as well. On land, its usually just plants.
In our local riparian (river) environments, periodic flooding clears out the ecosystem now and then. The first plants to recolonize used to be cottonwoods and willows. After a major flood in the 1990s, people were encouraged to plant butterfly bush (buddleia) to help hold riverbanks together.
After a flood, a river just has loose rocks and sand instead of organically rich material. Cottonwoods should come in first, along with a symbiotic bacteria that lives in its roots and helps it fix nitrogen. Cottonwoods have a central trunk and shed copious amounts of leaves in fall. Leaf litter leaches nutrients into the soil and holds water, helping to set the stage for plants that need more organic material to grow in.
Buddleia is a highly invasive species that originated in east Asian river systems. There, its not a problem but here, since its tolerant of drought at low nutrient levels, its become invasive. A butterfly bush will reach maturity in one or two years, and is capable of releasing three million seeds in a year that disperse by wind or water.
In our rivers, buddleias act differently than cottonwoods or willows, and thats what Jenn is studying. She has to ask questions that are answerable, rather than judgemental questions like, Is buddleia bad?
What is the roughness of buddleia? Roughness is a measure of anything that would obstruct a rivers flow such as meanders, obstructions, and vegetation. Buddleia are shrubs rather than trees and have a different impact on the rivers flow than trees do. They form dense canopies that shade out other plants. They interfere with the ordinary successional trajectory: By trapping sediment faster, they speed it up, and by shading out other plants, they slow it down, in a way that isn’t yet understood. A whole suite of plants that would ordinarily appear don’t get their chance.
In a river system, large woody debris is important. Pools form behind fallen trees and bars on which other plants can grow form. When buddleia crowds out cottonwoods, the large woody debris doesn’t come along in later years.
Jenn is also looking at the plants root system. Soil is held together by molecular attraction, water, and roots, so a change in the kind of roots dominating a rivers ecosystem would change how the soil acts.
Do we even need to want this noxious weed to vanish from the Northwest? Jenn is biased towards a yes answer. She gave us an arguments against her position, however.
Robert Pyle, a leading lepidopterist, is one of her opponents. He points out that butterfly species are declining due to pesticide use and loss of habitat. Butterfly bushes mitigate that loss somewhat. He says they are only found in highly disturbed waste areas such as railroad tracks, quarries, and the like. Why not let bees, butterflies, and ladybugs proliferate there too?
Bibliography:
Nesting habits of Light-Footed Clapper Rail in Southern California: http://elibrary.unm.edu/sora/JFO/v055n01/p0067-p0080.html
Zedler, Joy, Failure of wetlands restoration: http://www.blackwell-synergy.com/doi/abs/10.1111/j.1474-919X.2004.00333.x?cookieSet=1
Robert Pyle and butterfly gardening:
http://www.findarticles.com/p/articles/mi_m1169/is_n5_v32/ai_15638949
A rather intimidating article on Mannings equation: http://64.233.161.104/search?q=cache:yIrS9mWhaQkJ:streams.osu.edu/book/equation_pdf/Ch7-Equations.pdf+roughness+%22Manning%27s+equation%22&hl=enZNDSET2H
