World Wetlands Day is recognized on February 2, 2021 as a global celebration of wetland ecosystems, some of the most productive ecosystems of the world. The term “biological supermarkets” has been used to describe wetlands, given the immense biodiversity they support. Wetlands also provide several beneficial ecosystem services, including protecting and improving water quality, providing habitat for fish and wildlife, storing floodwaters, and maintaining surface water flow during dry periods.
Scientists estimate nearly 64% of the world’s wetlands have disappeared since 1990, a remarkable decrease coinciding with the spread of industrialization. In Canada, wetlands make up nearly 14% of the country’s landmass. The ecosystems were once considered wasteland—as a result, many wetlands have disappeared, overrun by roads, agricultural land, housing, and industry.
At Maplewood Flats, there is a network of four unique, yet interconnected constructed wetlands. Each wetland has distinct characteristics and biodiversity, yet they are all connected by streams and culverts. The wetlands at Maplewood Flats are a research priority for WBT, because:
- Wetland health can be used as an index to assess the general health of the broader conservation area; and
- Wetlands are essential to the surrounding terrestrial environment.
In 2020, Capilano University student Harrison Smith surveyed the wetlands and the aquatic macroinvertebrates in the Spring/Summer season, under the supervision of Capilano University professor Tom Flower, a board member of the WBT. Smith and Flower delivered a virtual presentation on their research in September of 2020.
Here, we present a synopsis of their research presentation.
Maplewood Flats wetland orientation
- Wetland one: Northernmost wetland, high canopy coverage, signs of otter habitation
- Wetland two: connected to wetland one through a stream, medium canopy coverage, smallest wetland
- Wetland three: connected to wetland two by a culvert, clear, shallow streams
Wetland four: connected to wetland three by a culvert, the southernmost wetland, the largest wetland, low canopy coverage and high sun exposure.
- Dissolved oxygen (DO) and temperature decrease from wetland one to four
- Species diversity increases from wetland one to four
- Elevated levels of copper and aluminum in the water, especially at wetlands one and two
- Presence of healthy, native aquatic and terrestrial plants: pondweed, duckweed, stargrass
- Presence of red alders and cottonwoods, typical for a previously disturbed site
- Presence of non-native species: Himalayan blackberry
- Narrow-leaved cattail detected (non-native species) in wetland three
- Wetland one macroinvertebrate species composition tilted toward “tolerant species”
- Wetland four macroinvertebrate species composition tilted toward “sensitive species”
- Overall, there are healthy assemblages of invertebrates present despite generally low water quality
- The pump water appears relatively clean, so metal contamination is likely coming from a different source
- The trend of increasing biodiversity from wetland one to four may simply be due to wetland size—wetland one is shallow and relatively small, whereas wetland four is bigger and deeper, hence has greater habitat diversity and can support more biodiversity
- Narrow-leaved cattails in wetland three may be efficiently removing copper, depending on seasonality
Recommendations and potential management tips
- Resolve copper contamination
- Repeat the survey in 2021 to develop and identify patterns and trends
- Compare the Maplewood Flats wetlands with an intact wetland (reference site): Identify a wetland that has NOT been previously disturbed in similar Pacific northwest, coastal conditions and compare to gain an understanding of what we should be seeing at Maplewood Flats
- Boost oxygen for vertebrates, but not for fish
- Improve wetland depth and openness across wetlands one to three to increase biodiversity; however, this could be detrimental to species currently living there.