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Archive for January, 2016

A thicket of Japanese knotweed. Citation: Tom Heutte, USDA Forest Service, www.invasives.org

A thicket of Japanese knotweed. Citation: Tom Heutte, USDA Forest Service, http://www.invasives.org

 

Fallopia Japonica – known commonly to the conservation community as Japanese Knotweed is an invasive riparian zone plant. Infestations of knotweed typically invade disturbed areas along streams and rivers and can quickly become overwhelming. What is more, the extensive underground root network make complete irradiation quite a task. Knotweed infestations are notorious for taking numerous years of persistent efforts to control.

 

Not only is knotweed difficult to control once it gains a foothold, it is finding an easier route to gaining a foothold in recent years, especially in the north country, where washouts have been occurring with greater frequency than ever before. As more and more of the region has become developed, farm fields, roads and other structures have come to abut with the water’s edge, removing critical riparian habitat. Furthermore, when the streams overflow their banks, they often carry the plant material away from the edge, as soil erodes in the turbulent waters.

 

Riparian buffers are critical habitat. For one, riparian root systems help to hold stream banks together during minor floods, and create a protective buffer for the more flood sensitive habitat beyond the flood plain. Knotweed, on the other hand, does little to hold banks together, and promotes erosion of stream banks to a much greater degree than our native riparian plants. Once erosion occurs, the most likely plant to return to the bank is the knotweed, (which in many cases exacerbated damaging floods in the first place).

 

The other important role for riparian habitat is that it helps to filter pollutants out of runoff, before they enter the water supply. This is a critical role in the Champlain Valley, where agricultural runoff is a huge problem.

 

In recent years, Lake Champlain has seen beach closures, and increased monitoring of drinking water intakes, due to blue-green algae blooms. The lake often sees elevated levels of the cyanobacteria, which can cause skin irritations, liver damage and neural tissue damage. The algae blooms are common on all larger bodies of water, but particularly in Lake Champlain the algae is aided by phosphorus in agricultural runoff.

 

In other watersheds, such as that of the Delaware Bay or the Gulf of Mexico, similar problems with agricultural runoff have led to agal blooms sucking oxygen out of the water, leading to oceanic dead zones, where fish life cannot survive. This may end up being the fate of Lake Champlain, if the algal blooms cannot be reigned in.

 

The issue illustrates the interconnectedness of watersheds. Extensive knotweed infestations upstream aid the entrance of agricultural fertilizers into the lake waters, by impacting the riparian buffer areas. To solve the algae problems, you have to solve the problem of disappearing riparian buffers and thus the infestations of knotweed. While a stream side infestation may not seem like a problem worth tackling aggressively, it affects both human health and the ecosystem health downstream. This is just one example of why it is immensely important to protect the ecosystem services provided to our watersheds by the healthy functioning of riparian buffers.

 

The easiest defense against knotweed is prevention. For farmers, this involves developing realistic buffers, rather than planting or grazing cattle up to the water’s edge. These buffers, once in place, also provide crop protection, on top of helping to outcompete aggressive knotweed infestations. Roads should also be planned to include a buffer area. Often times, in Vermont especially, roads are placed in stream valleys because it is the easiest, latest place for a road. However, as recent floods have shown, these sections of road often washout in floods, and are costly to repair. It is better, then, to take on the initial building expense, and build the roads in more sustainable locations, with hydrology better accounted for. Since riparian zones help to stabilize banks, this can also help to protect the roads from the periodic washouts.

 

As climate changes, and we see more and more deluges washing out the north country, it is ever more important to develop protective buffers that realistically consider the changing nature of streams. Flood plains and ephemeral wetlands need to be better accounted for, so that the floods that do occur will be less devastating to infrastructure.

 

If these best practices are more widely instituted, we will found ourselves more prepared for what is inevitable.

 

 

http://healthvermont.gov/enviro/bg_algae/weekly_status.aspx

http://www.burlingtonfreepress.com/story/news/2015/07/14/warm-spell-triggers-cyanobacteria-alerts-in-lake-champlain/30131655/

http://oceanservice.noaa.gov/facts/deadzone.html

 

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