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A riparian zone or riparian area is the area between the land and a river or stream. Riparian zones are important in performing many functions and roles in an ecosystem such as soil stabilization, water filtration, wildlife habitat, and natural irrigation. Riparian zones vary in plant types and wildlife from location to location. These areas are being impacted by humans which is altering the way these areas function. Restoration and repair is being performed on damaged riparian areas to help restore them to their natural state.

Characteristics
Riparian zones are the area between a water environment and a terrestrial environment. These areas can occur along natural waterways or man-made bodies of water. Riparian zones often have plants and wildlife that are unique due to the amount of water present in these areas from elevated water tables. The body of water that the riparian zone is next to often plays a role in shaping the riparian zone. Riparian zones along streams and rivers may be more influenced by the waterway because streams and rivers are more dynamic than other aquatic environments, like ponds and lakes. Definitions of riparian zones vary and can limit the area of a riparian zone to just the edge where the water and land meet or the definition can be very broad and include a much larger area of land. Riparian zones do not make up a large portion of land compared to other environments, but they are still important because of the roles and functions they have in the ecosystem.

Roles and functions
Riparian zones can preform many functions in an ecosystem. One function that riparian zones play a role in is reducing soil erosion. Riparian zone vegetation and root systems can slow the flow of water running over the soil. This helps reduce soil erosion and flood damage by causing less soil to be washed away in heavy precipitation events. The roots of plants in riparian zones also perform many functions. The plant roots can trap sediments which reduces suspended solids entering the waterway creating less turbid water. The roots can also replenish soils with trapped nutrients and help build stream banks by stabilizing the land. Riparian zones are important to nutrient cycling and can help store and move nutrients in and between aquatic and terrestrial environments.

The riparian zones are also important to provide wildlife habitat for aquatic and terrestrial organisms leading to a increase in biodiversity in riparian areas. These areas provide food, shelter, and water for many organisms. Riparian zones are critical for the fish that live within rivers, such as brook trout and char, because they provide shelter and protection from predators. Riparian zones can also serve as wildlife corridors, enabling aquatic and terrestrial organisms to move along river systems and avoid isolated communities. This helps organisms to migrate easier from one place to another and therefore can increase the biodiversity of the area.

Riparian zones can provide irrigation to crops and to native plants. Riparian zones help to retain groundwater which can then be used by native plants as a water source. This ground water can also be used in irrigating crops in areas that are arid or semi-arid. Riparian zone groundwater also plays an important role in carbon transport from terrestrial ecosystems to aquatic ecosystems. Groundwater from riparian areas can also be used as a source of drinking water for people to use. From a social and economic perspective, riparian zones can increase nearby property values, increase aesthetic views, and can bring about entertainment opportunities. People who live near a riparian zone often have access to rivers or streams which allows for fishing, swimming, and boating.

Finally, riparian zones are important in the process of filtering water. Riparian zone vegetation can help to filter out excess nutrients and pollutants such as organic waste, pesticides, and fertilizers. Research shows that riparian zones are instrumental in water quality improvement for both surface runoff and water flowing into streams through subsurface or groundwater flow. Riparian zones can play a role in lowering nitrate contamination in surface runoff that would otherwise damage ecosystems and human health. Particularly, the attenuation of nitrate, or denitrification of the nitrates, from fertilizer in this zone is important. The use of wetland riparian zones shows a particularly high rate of removal of nitrate entering a stream and thus has a place in agricultural management. Because riparian zones can act as a filter, they can also act as a buffer zone lessening the impacts of climate change and increased runoff from urbanization. Factors such as soil types, root structures, climatic conditions, and vegetative cover determine the effectiveness of riparian buffering. Overall, riparian zones play an important role in ecosystems and provide many ecosystem services to their surrounding environment.

Vegetation
The assortment of riparian zone vegetation varies from those of wetlands and typically consists of plants that are either emergent aquatic plants, or herbs, trees and shrubs that thrive in proximity to water. Vegetation in riparian zones also varies based on location. Listed below are some common vegetation found in riparian zones in North America, Asia, Australia, and Central Europe.

Water's edge
Herbaceous Perennial:
 * Peltandra virginica – Arrow Arum
 * Sagittaria lancifolia – Arrowhead
 * Carex stricta – Tussock Sedge
 * Iris virginica – Southern Blue Flag Iris

Inundated riparian zone
Herbaceous Perennial:
 * Sagittaria latifolia – Duck Potato
 * Schoenoplectus tabernaemontani – Softstem Bulrush
 * Scirpus americanus – Three-square Bulrush
 * Eleocharis quadrangulata – Square-stem Spikerush
 * Eleocharis obtusa – Spikerush

Western
In Western North America and the Pacific Coast, the riparian vegetation includes:

Riparian trees Riparian shrubs Other plants
 * Sequoia sempervirens – Coast Redwood
 * Thuja plicata – Western Redcedar
 * Abies grandis – Grand Fir
 * Picea sitchensis – Sitka Spruce
 * Chamaecyparis lawsoniana – Port Orford-cedar
 * Taxus brevifolia – Pacific Yew
 * Populus fremontii – Fremont Cottonwood
 * Populus trichocarpa – Black Cottonwood
 * Platanus racemosa – California Sycamore
 * Alnus rhombifolia – White Alder
 * Alnus rubra – Red Alder
 * Acer macrophyllum – Big-leaf Maple
 * Fraxinus latifolia – Oregon ash
 * Prunus emarginata – Bitter Cherry
 * Salix lasiolepis – Arroyo Willow
 * Salix lucida – Pacific Willow
 * Quercus agrifolia – Coast live oak
 * Quercus garryana – Garry oak
 * Populus tremuloides – Quaking Aspen
 * Umbellularia californica – California Bay Laurel
 * Cornus nuttallii – Pacific Dogwood
 * Acer circinatum – Vine Maple
 * Ribes spp. – Gooseberies and Currants
 * Rosa pisocarpa – Swamp Rose or Cluster Rose
 * Symphoricarpos albus – Snowberry
 * Spiraea douglasii – Douglas spirea
 * Rubus spp. – Blackberries, Raspberries, Thimbleberry, Salmonberry
 * Rhododendron occidentale – Western Azalea
 * Oplopanax horridus – Devil's Club
 * Oemleria cerasiformis – Indian Plum, Osoberry
 * Lonicera involucrata – Twinberry
 * Cornus stolonifera – Red-osier Dogwood
 * Salix spp. – Willows
 * Polypodium – Polypody Ferns
 * Polystichum – Sword Ferns
 * Woodwardia – Giant Chain Ferns
 * Pteridium – Goldback Ferns
 * Dryopteris – Wood Ferns
 * Adiantum – Maidenhair Ferns
 * Carex spp. – Sedges
 * Juncus spp. – Rushes
 * Festuca californica – California Fescue bunchgrass
 * Leymus condensatus – Giant Wildrye bunchgrass
 * Melica californica – California Melic bunchgrass
 * Mimulus spp. – Monkeyflower and varieties
 * Aquilegia spp. – Columbine

Asia
In Asia there are different types of riparian vegetation, but the interactions between hydrology and ecology are similar to the way it occurs in other geographic areas.
 * Carex spp. – Sedges
 * Juncus spp. – Rushes

=== Australia === Typical riparian vegetation in temperate New South Wales, Australia include:
 * Acacia melanoxylon – Blackwood
 * Acacia pravissima – Ovens Wattle
 * Acacia rubida – Red Stem Wattle
 * Callistemon citrinus – Crimson Bottlebrush
 * Callistemon sieberi – River Bottlebrush
 * Casuarina cunninghamiana – River She-Oak
 * Eucalyptus bridgesiana – Apple Box
 * Eucalyptus camaldulensis – River Red Gum
 * Eucalyptus melliodora – Yellow Box
 * Eucalyptus viminalis – Manna Gum
 * Kunzea ericoides – Burgan
 * Leptospermum obovatum – River Tea-Tree
 * "Melaleuca cuticularis" – Saltwater paperback
 * Melaleuca ericifolia – Swamp Paperbark

Central Europe
Typical riparian zone trees in Central Europe include:
 * Acer campestre – Field Maple
 * Acer pseudoplatanus – Sycamore Maple
 * Alnus glutinosa – Black Alder
 * Carpinus betulus – European Hornbeam
 * Fraxinus excelsior – European Ash
 * Juglans regia – Persian Walnut
 * Malus sylvestris – European Wild Apple
 * Populus alba – White Poplar
 * Populus nigra – Black Poplar
 * Quercus robur – Pedunculate Oak
 * Salix alba – White Willow
 * Salix fragilis – Crack Willow
 * Tilia cordata – Small-leaved Lime
 * Ulmus laevis – European White Elm
 * Ulmus minor – Field Elm

Human Impacts
Riparian zones are important ecological areas that are being impacted by humans in many ways. Riparian zones are important to the environment around it and changes to the roles and functions they perform can have a major impact on the land and the environments around the affected riparian zone. Deforestation and overgrazing of these areas is one of the ways humans are having an impact. Clearing of these riparian zones can cause a decline in healthy vegetation impacting the riparian's zone ability to filter water. When land in a riparian zone is cleared it allows for more soil erosion and has major effects on the macroinvertebrate communities in streams. Deforestation does not only impact the living parts of a stream, it can also change stream channel morphology, or the way water flows, due to the changes in runoff and soil erosion. This can then impact the aquatic wildlife in the affected area altering the food webs of that ecosystem. Other factors such as the introduction of new species, human population growth, and the demand for more natural resources are also having an impact on riparian zones.

Repair and Restoration
Many riparian zones have been damaged and research is being done on the best way to restore them. Often repairing these areas is difficult because the source of degradation is not always addressed complicating the repair. Restoring these areas also becomes complicated when there are conflicting interests about how the land in riparian areas should be used. Riparian areas are often damaged by vegetation removal or a loss of water caused by water withdrawals or water rerouting. The goal of restoring riparian areas is to bring back the ecosystem services that once occurred such as filtering water and providing wildlife habitat. Impacts on riparian zones can affect organisms living in these areas, and restoration is not always sufficient to recover their populations.

Restoration efforts vary from site to site. Restoration of riparian areas most often involves looking at the hydrology of the area and replanting native species that have been destroyed. One riparian restoration project was conducted in California on an area known as Cottonwood creek. The riparian zones in this area had been destroyed by deforestation, excessive flooding and invasive species. The project was completed in 2005 and the area was restored by mapping local riparian areas, planting native riparian plants, improving the drainage of water, stopping behaviors that damaged riparian areas and educating the public. The project was able to repair some of the riparian areas and improve water filtration in the local area. A restoration project was also conducted in Cottonwood Canyon in Oregon which as had some success in restoring function to the damaged riparian areas.

Studies are being conducted on how effective these restoration efforts are at restoring an area back to its original state. One study found that vegetation will respond to repair efforts within a few years, but soil quality was shown to not respond within that time frame. Restoration efforts in riparian areas are beneficial to the environment, but may not be successful at returning the area to its original state before it was degraded.

Protection
Riparian areas do not have a direct law that protects them from being destroyed in the United States, however many of the riparian lands in the United States are owned by the government and are therefore protected. In some states such as California, a permit is needed to build within thirty meters of a body of water in designated areas. These permits help to ensure that nothing is done to damage areas around water bodies which indirectly protects riparian areas. There are options for protecting riparian areas directly that are being considered. These include identifying and protecting existing riparian areas, provide financial incentives for protecting riparian areas, regulate activities on publicly and privately owned riparian areas and to purchase privately owned riparian lands so that they can be protected and managed by the government.