why are invasive blackberries bad?

[rex-craft7]

i went out today to get some exercise and do something useful at the same time by volunteering at a local tree hugging/planting/trail making sort of organization. i had never done this sort of thing, but we (the volunteers) met up at a local park, and we spent the day killing blackberries. the whole time, i was wondering why i was doing it.

 

after a quick internet search at home, i found that the species we were removing were Himalayan blackberries, which are apparently overrunning the NW (i live in seattle)

 

from first glance, it looked like they were taking over the local tree/brush so that the area would turn into basically a mass of bramble bush - so it would change the local ecology. but that sort of thing happens all the time, so im still wondering why these invasive plants need to be killed - how much damage exactly do they do?

[UC]

Species native to an area are generally in a very delicate balance. There are forests a short drive from my house that at one point had an understory entirely composed of magnolia. However, white tailed deer eat the seedlings and destroy saplings. I took a several mile walk through the woods and found a single stunted magnolia. Flocks of birds depended on the oily magnolia fruits for energy. Now, thorny, toxic barberry has taken over the open spaces. Nothing eats the plant itself, but the birds eat the fruit, which have virtually no nutritious value. The bird population has declined in the area and the barberry spread even more rapidly as a result of bird dispersion. Invasive species are invasive for a reason. They grow fast, spread rapidly, are often toxic or thorny, and have little food value to native species. Even tall maple trees in the area are not the natives. They are mostly norway maple now. These are resistant to diseases and produce huge quantities of viable seeds. They've wiped out the native hardwoods and grow thickly enough that the ground beneath them is literally bare except for a few japanese stiltgrass plants, which choke out anything growing on the ground elsewhere.

 

These woods have not been cut since colonial times. There is an unfortunate clause in the deed (the land was donated to a local college) that prevents them from intervening to save the woods. The sentiment when it was written was that the woods will stay as is if left alone, but this was before many invasives were around, something the deed-writers could not have forseen. Now everything around the wooded area has been cut down and it's overrun with invasives. The woods are literally sick and it's depressing to see because nobody can do anything about it.

 

We are losing ecological diversity and a piece of history. There's also something beautiful about a healthy forest. It's something you'd want around for future generations to be able to see. In this particular forest, it is also a valuable research tool. The invasives make it harder, but studying what's left of the natives helps archaeologists better understand the past. In this particular area, it is quite unusual that there is an old growth stand at all given the suburban development around it. These natives are the resources that prior generations had available to them in the area. Studying the invasives themselves can help, even though they can't be removed at this point. Better models of their growth and spread are available through study which will be valuable elsewhere. It's making the best of an unfortunate situation.

Edited February 8, 2009 by UC

[Phi for All]

Moved from General Discussion to Ecology and the Environment.