Written by Karen Munro, M. Sc., Environmental Scientist
More ramblings about connections between healthy lives and healthy watersheds, this time about habitat. Habitat is a fancy term for “where we live” – habitat provides food, water, shelter, space. Imagine a hamster cage. Every organism has a habitat, even humans, although we can feel quite disconnected from our habitat.
A watershed is all the land that drains into a body of water. The Mississippi River watershed may cover half the United States (that’s a guess). Several watersheds might snuggle up in a coastal town.
When we think about stream habitat, we can think of the many animals that live there, what they need, how they interact and adapt. Natural streams are a wonder, in that they provide all the ingredients needed by the organisms that live there. Stream environments contain substrates (stoney, sandy or silty bottoms), pools, riffles (faster flowing areas), and stream bank vegetation. These areas are highly productive, with high biological diversity (biodiversity), like other interface environments, for example the edge of a pond, the seashore, an estuary where fresh water meets the sea, the fringe between meadow and forest. While these areas can be thin bands or interconnecting habitats, they are unique environments that support large amounts of life.
Streambank vegetation provides many benefits to the aquatic species and birds and wildlife that flock there:
- shade to cool the water;
- leaf litter to feed stream and terrestrial insects;
- roots to stabilize the banks and prevent erosion;
- instream woody debris to provide varied niches for many organisms;
- berries, seeds and roots for birds and wildlife;
- a great spongy soil to absorb and slowly release water to the stream, purifying the water in the process.
The same characteristics that make streams and river valleys so attractive to wildlife make these areas attractive to humans. What a joy to walk a forest trail and come upon the coolness of a stream, small brown birds flitting through the branches, a canopy above, the mysterious sound of water tumbling over boulders or the deep slow majesty of the river. We feel purified and energized in such places. If the path hasn’t been compacted by too many travelers, we will reap the benefits of the extra bounce in our step from the spongy soil.
There are threats to such places, particularly as cities grow and farmland or mountainsides turn into suburbia. Here are just a few:
- sediment loads from poorly designed construction projects silt up spawning gravel for fish and degrade stoney habitat needed by pollution sensitive insects (mayflies, stoneflies, caddisflies, these are a food source for birds and fish), turning the water murky or grey;
- a steady march of invasive plants from garden to stream (in my neck of the woods, these include English ivy, Japanese knotweed, Himalayan blackberry, Scotch broom, Eurasian milfoil, holly – note the strange geographic and cultural references, none of them Pacific or even North American);
- landscaping with lawns and ornamental species, leaving the stream exposed to the heat of the sun;
- culverts that allow road crossings but prevent migration of fish, squeezing the water so in times of rain it constrains the water like a firehose;
- channelization (straightening of the stream and armouring the banks with large rock known as riprap), historically done in the name of flood protection, but now known to make flooding problems worse;
- burying of headwater tributaries to make way for more houses;
- removal of valuable estuary and valley bottom land because it is flat and useful for human activities; and
- fragmentation of green spaces, making it difficult for migratory birds and large mammals (deer, bears) to use the areas they call home.
As with water quality issues (Part 1), there are many things we can do, ranging from individual efforts to maintain native vegetation on our own property and community days to remove invasive plants (ivy pulls, broom sweeps, etc.), to lobbying local governments to preserve streamside areas through zoning, bylaws and covenants.
The websites below provide information specific to British Columbia, but also have links to organizations across North America:
Websites of the many conservation organizations also provide great information and local links.