Sedges & ecosystems
It is not widely known that Sedges have considerable economic and ecological importance.
Sedges, the Cyperaceae family, have a reputation for being incredibly difficult to identify and often the uninitiated when asked to identify them will call them grasses (see What are sedges?) so it is perhaps not surprising that it is not widely known that they have considerable economic and ecological importance.
Sedges are among the largest and more diverse families of herbaceous plants and although they resemble grasses they are not closely related and have many different characteristics particularly in the structure of their flowers.
They have a diverse distribution and can be found in all parts of the world except Antarctica. They grow in a broad range of habitats and altitudes, from the Arctic tundra through to temperate and tropical regions and are predominant plants in many wetlands. They also like man-made habitats such as canal banks and ditches.
Sedges are the major (often dominant) plant of many wetland ecosystems throughout the world, both tropical and temperate. Here their long, strong densely tangled rhizomes and roots can help in erosion control and the improvement of water quality by acting as filters to remove pollutants and sediments. Water treatments using sedges have demonstrated removal of a large percentage of nitrogen and significant sequestration of metals such as copper.
Sedges are especially important in wetland food chains. Submerged sedges provide habitat structure for diverse riparian invertebrates that many other species of animals are dependent upon and their fruits and sometimes their shoots and tubers are important foods for many aquatic and amphibious animals. Their leaves are often used as nesting material and some species provide shelter and nesting sites for species of birds and mammals.
Once sedges die they provide food for many aquatic invertebrates. Sedges are grazed by small animals and their seeds consumed by waterfowl and small birds.
Fish also rely on sedges that provide cover at stream and river edges for salmon, trout and other coldwater species. .
Although sedges are important plants for economies and ecosystems it must be pointed out that some species affect human economies because they are weeds and two of them are among the world’s worst weeds – Purple nut sedge (Cyperus rotundus) and Yellow nut sedge (Cyperus esculentus).
Purple nut sedge infests crops throughout tropical and warm temperate regions of the world competing robustly for soil, moisture, nutrients and for light in the case of low-growing or slow-starting crops. Yellow nut sedge is a serious threat in cooler climates causing substantial crop loss.
Some sedges such as the Umbrella sedge (Cyperus iria) and Smallflower umbrella sedge (Cyperus difformis) are significant weeds in rice paddy fields damaging their productivity whilst several coarse species are considered severe pasture weeds reducing the land’s grazing quality with their tussocks of harsh, inedible foliage.
Sedges are of prime importance in conservation as many wetland ecosystems are severely threatened by human activity and some species may be in danger of extinction. It is important therefore that sedges, those that are adapted to live in both wet and dry environments, are identified and understood for the future protection of fragile ecosystems.
References: Royal Botanic Gardens, Kew; Encyclopaedia Britannica; aob.oxfordjournals.org; Role of Sedges (Cyperaceae) in Wetlands and their Economic, Ethno-botanical Importance, Sanjay Mishra and Devendra Kumar Chauhan; University of Reading, reading.ac.uk/centaur.