Blog Post #42 – Healthy Aquatic Ecosystems

Healthy Aquatic Ecosystems


Healthy aquatic ecosystems are fundamental to achieving watershed security, as they are important to the wellbeing of all living things and can help buffer communities from extreme climate events. Individually and cumulatively, impacts from land use and pollution, water use pressures, and climate change are some of the biggest threats to aquatic ecosystems.

Aquatic ecosystems

Aquatic ecosystems are comprised of the plants and wildlife that live in, on, or near water. An aquatic ecosystem is made up of streams, stream channels, wetlands, and riparian areas, together with their living components.  Pressures on these systems result in significant impacts to aquatic environments.  For example,

  • Wetlands make up about 7% of B.C. and are relied upon by around 500 species, including numerous species at risk. Wetlands have been declining in B.C. since the 1900s. In the Okanagan alone, over 85% of wetlands have been lost since 1900.
  • Riparian areas – those areas of transition from the water edges to forests – are essential for aquatic life, providing a wide range of ecosystem services such as shade, food, habitat, water quality, bank stability, etc. Approximately 80% of B.C.’s wildlife directly dependent on riparian areas or use them more than other habitats.

Linkages between upland and riparian ecosystems are essential for wildlife.  In some instances, development and road building in watersheds can fragment and isolate habitat, possibly resulting in localized extinctions.

Land uses – riparian disturbances and water pollution

Land uses may result in riparian disturbances and associated pollution, and can be one the biggest threats to water quality for aquatic ecosystems. Land use and riparian area disturbances affecting vegetation around waters can be temporary, or sometimes permanent, and may affect key ecosystem services.  Water pollution from point source (e.g., wastewaters, sediment) and non-point sources (e.g., fertilizers, runoff) can increase aquatic exposures to metals and synthetic chemicals which can reduce growth, impair reproduction, affect immune systems, and/or directly kill aquatic species. Studying the impacts of land use on aquatic ecosystems will help refine regulatory and scientific tools that may be used to prevent or mitigate the impacts of land use disturbances and pollution.

Water Use Pressures

Environmental flow needs (EFNs) is a term used to describe the volume and timing of water required for the proper functioning of an aquatic ecosystem. Many streams in B.C. experience periods of low streamflow during the summer, and many aquatic ecosystems have evolved to adapt accordingly as part of the natural variability in a system. However, in some areas, humans have taken large volumes of surface water and/or groundwater and altered the natural environment, particularly in periods of drier than normal weather. The introduction of the Water Sustainability Act (WSA) provided government decision-makers with the regulatory tools to consider EFNs when authorizing water use.

We must increase our understanding of the following to better inform the development of tools to maintain EFNs for aquatic ecosystems:

  • Natural streamflow regimes and trends,
  • Needs of aquatic ecosystems,
  • Which watersheds and aquatic ecosystems are most vulnerable to low streamflow conditions.

Climate change

Climate change is expected to further the impact timing, magnitude, length of droughts and floods and extreme events. Healthy aquatic ecosystems play an important role mitigating the impacts of climate change on communities. Improving our knowledge of ecosystems services and, in response, sustainably managing the natural assets within a watershed can increase the health and resilience of all living things.