Where wood debris accumulations are heaviest, marsh vegetation can be completely displaced, resulting in loss of habitat for salmon, other fish and invertebrates. Decomposition of debris can reduce oxygen concentrations and increase toxic accumulations of hydrogen sulphide. River Works volunteers remove wood debris by hand from wetland areas and put it into dumpsters, which are taken to a fibre recycling plant. Non-native vegetation River Works has focused its efforts on reducing and controlling the impacts of purple loosestrife and scotch broom at its sites. These plants are cut at the base and then disposed of off-site.
Purple loosestrife is a tall plant with bright purple spiked flowers.
It is likely this plant was introduced from Europe about 200 years ago through ballast water, livestock feed or intentional plantings for horticultural uses. It has spread quickly and become a noxious weed it many wetland areas. Scotch broom is a spindly shrub with bright yellow flowers and seedpods that grows in disturbed areas such as on the side of highways. The plant was introduced in 1850, when three plants were planted on Vancouver Island. In areas where scotch broom and purple loosestrife have invaded, there is a lack of biodiversity, as native plants are crowded out.