At Fresh Landscape Design we have a strong interest and focus on creating healthy environments for people, plants and animals. Soil and water testing can be expensive and beyond the needs and resources of many people. A great, low cost and practical way to monitor and support the sustainability of your designed landscape is to incorporate bio-indicator plants and animals.
Plants can be used as a quick and easy way to monitor nutrient levels, or to remove excess or unwanted nutrients from a system. Companion planting arrangements can be used to help create the conditions that each species needs in order to thrive. Keeping an eye on the animals that visit and live in your site can also act as a check on whether the overall space is healthy, and provide an early warning should something go wrong.
Hydrangeas are a perfect example of a bio-indicator plant. Aluminium is necessary to produce blue flowers and there is sufficient aluminium in most soils to get blue flowers. If you have alkaline soils (high pH) the aluminium is not available for the plants to use. Pink Hydrangea flowers indicate alkaline soils. Camellias on the other hand prefer acidic soils (low pH). Plant your camillias where you get blue hydrangeas for best results. They will enjoy sharing the moist protected location as well.
Algae can be a good indicator of water quality and can react rapidly to changes in levels of nitrogen and phosphorus. Algae blooms are a sign that the balance in the system is unstable and the causes need to be investigated and resolved.
Some plants are bio-accumulators of particular nutrients. These plants are good at taking up and removing one or more nutrients from the soil. For example, Lomandras take up phosphorus and could be planted with species such as Grevilleas that don’t like this nutrient. This principle has been used to remediate contaminated sites using plants.
Permanent or ephemeral wetlands are ideal spaces for the inclusion of bio-indicator plants. Wetlands are places where nutrients and pollutants collect, so they should include plants that help you to monitor these conditions. Fish, frogs and many insects are sensitive to their environment. The health of these populations on your site is a strong indication of things going on that you otherwise couldn’t see. Knowing what to look and listen for is a great place to start.
These principles were used in my student design project for the Cherbourg Materials Recycling Facility in Queensland while I was studying at the University of Canberra. One of the most important design considerations was to produce a low cost, low technology and low maintenance system to minimise the environmental impact of the proposed operation, particularly air and water pollution. Solutions were needed to reduce, remove and monitor for odours, particulates, nutrients and sediments. Visual impacts for nearby residents also needed to be minimised.
Here is a list of strategies used in the design.
- Replication of natural wetland system, incorporating multiple ponds and ecosystem zones, to filter nutrients and sediments from water prior to water leaving the site. Reeds and rushes catch sediments and remove nutrients from water.
- The use of bio-indicator animals to monitor environmental health by stocking holding dams with fish to provide a rapid and obvious assessment of water quality. Species indigenous to the area were chosen to maximise their chance of survival and minimise the potential to create a greater environmental problem should they escape.
- Create habitats using native indigenous plants. Encourage local species to colonise, increasing biodiversity and encouraging resilience. Monitor populations of frogs, birds, lizards and mammals as indicators of environmental health.
- Positioning of vegetation buffers both up and downwind of prevailing breezes. This disrupts the wind so odours don’t carry, catches any particulates that happen to be blown around and creates a living visual screen from neighbours.