Improvements to river habitats can be the key to saving species from extirpation by helping them sustain healthy populations. Habitat improvement is especially important to previously degraded areas which have already seen declines in species. There are many methods of habitat improvement, most of which aim to undo damage caused by humans.
Artificially straightened channels can cause many problems for wildlife, as explained in our habitat loss article. Re-meandering a river can combat these issues by restoring a river to its more natural state. It can be done by removing vegetation and bank material at short intervals, or by putting material like logs into the channel that alter the flow of the water. This encourages a sinuous channel which is a more diverse and therefore better habitat for many species.
Re-meandering larger rivers or streams can be very expensive as it requires the movement of large amounts of bankside material. Occasionally the river will re-meander itself as trees and other woody material naturally fall in its path and change flow dynamics.
Fish passages allow fish to travel past blockages in rivers so they can continue their life cycles and successfully breed. These blockages are usually dams built for industrial purposes and the creation of fish passages are an alternative to dam removal when that is unfeasible. There are a number of different types of fish passage including simple bypass channels that carry a small flow around the blockage, as well as more complex methods like river elevators which lift fish upstream.
Back channels/fish refuges
A back channel is a small extra channel that is created, connected the main channel. They are created because they are areas of slow flowing water that provide habitat for a range of species. Back channels may be created solely as fish refuges in areas where fish populations are struggling. Fish refuges may also simply be small areas dug next to the channel to which juveniles can escape from fast flows.
Creation of new ponds is an excellent way to improve local habitat. Most existing ponds are heavily polluted and this has a hugely negative impact on freshwater life. New ponds give cleaner, better habitats which have positive impacts on the surrounding local wildlife as well as within them. They support many of the UK’s most endangered species and so more similar habitats are needed to increase stability of populations. New ponds can be located in areas where they are at low risk of pollution to ensure they have the maximum benefit. Creating scrapes, which act as temporary ponds, is also a great way of keeping the floodplain wetter for longer and encouraging biodiversity.
Large woody debris, previously seen as a nuisance that caused problematic blockages to river channels, is now recognised as a benefit to conservation. It includes branches and trees that have fallen into rivers that often accumulate into dams. Woody debris alters the flow of the river and can have great benefits with regard to improving degraded rivers and flood defence. The slow flows that the debris creates help to stabilise pool riffle sequences which are ideal habitat for many species. It is also one of the cheapest, most natural, and easiest options for habitat improvement. Woody debris makes a good habitat in itself as it provides shelter from strong flows and protection from predators, as well as influencing wider reaches. All types of animals have uses for it – aquatic invertebrates use it to emerge from their larval stages and use the range of surfaces to colonise, and birds, amphibians, and mammals use it for perching and foraging.
Wetlands are waterlogged areas which support hugely biodiverse communities. They are especially important for birds because they are occupied by so many invertebrates which they prey on. Reed beds are usually planted to allow nesting and foraging of wading birds. The number of wetland habitats has quickly depleted due to the increased need for infrastructure, which is why more of these incredibly important areas need to be created. It can be difficult to find large areas suitable for new wetlands, but they are considered one of the best and most productive types of habitat. They can also play a role in trapping pollutants which is why more are desperately needed.