Wetlands

Agronomy: How to look after wetlands on your farm

Wetlands, which are home to a wide variety of fish and wildlife, can also be the lifeblood of farmers in low-rainfall areas.

Wetlands – located along the shores of oceans, lakes, rivers and streams – protect properties surrounding these areas against flooding by ‘sponging’ up and storing excess water. They also act as a filter by removing impurities such as heavy metals and pathogens (such as bacteria and viruses) from runoff water. In fact, research has shown that some wetlands are actually capable of removing 85-90% of phosphorus and nitrogen from runoff water.

Wetlands are home to a wide variety of fish and wildlife species. They prohibit soil erosion and it is therefore extremely important that farmers protect this valuable resource.

What is a wetland and how does it work?

Wetlands are often described as giant sponges that absorb water from a variety of sources during wet periods. The collected water is slowly released during dry periods. This reduces flooding, thereby easing the impact of drought and of recharging valuable groundwater supplies.

Wetlands consist of uplands as well as riparian and aquatic zones. Uplands are the dry land surrounding a wetland; the riparian zone is the strip of land and vegetation between the higher uplands and the shallower, wet areas. The latter are usually heavily vegetated with various types of plants. The aquatic zone is the wet area of the wetland and can either be deep, with lots of open water, or shallow, with no open water.

Protect your wetland as follows:

Agriculture

Ground water

Large areas of land are usually cleared around wetlands for agricultural purposes. Because agriculture is such a water-intensive industry, it is essential that farmers regularly monitor ground water. Levels drop during low-rainfall seasons due to reduced recharge. Ground water can, however, still be accessed by deep borehole pumps, which means that the water table is drawn even deeper, which has a negative impact on the environment and ultimately on the recharge of the
water table.

What can I do to help?

  • Monitor your ground water use and levels regularly.
  • Provide accurate information to your local Water Users Association (WUA) to ensure sustainable management by all; and support your local WUA.

Canals

Canals are used to divert water flowing into a drainage furrow and often lead to the dehydration of wetlands, an overgrowth of vegetation (including invasive alien species), and disruptions to the flow of water through wetlands, which can weaken its functioning (preventing erosion and flooding, and acting as a water filter and purifier), reduce soil organic matter and increase the risk of underground fires and soil acidity.

What can I do to help?

  • Assess if historic canals are present on the farm.
  • Plug all canals to avoid erosion and to encourage re-wetting of wetland.
  • Contact your local Working for Wetlands agent for extension support.
  • Use water-efficient pipelines as an alternative to canals.
  • Avoid future wetland channeling.

Ground water contamination

It is possible for ground water to be contaminated, because agricultural chemicals enter the system and are released back into the water. This often results in the death of birds, fish and plants. Nitrification also promotes the abnormal growth and abundance of certain water-plant species. Buffer strips between land and natural water streams and wetlands are recommended to minimise the contamination potential
of chemicals.

What can I do to help?

  • Incorporate buffer strips; 50-70 meter strips are usually recommended.
  • Follow best practice regarding the fertilisation of agricultural fields in order to prevent possible ground water contamination and effect savings on production costs.
  • Know your soils by undertaking regular soil sample monitoring.
According to Cape Nature some of the biggest threats to wetlands are: Lack of best practice in agriculture, climate change and invasive alien species.


Grazing practices

Wetlands are often used for grazing because they are surrounded by vegetation. But overstocking can result in hardened soil and reduced plant cover, which cuts down on water infiltration and ground-water recharge. Also, animal hooves can damage root systems and trampling destroys the plant cover that inhibits winter erosion. It is essential, therefore, that farmers control livestock numbers and grazing times during the drier months.

What can I do to help?

  • Stick to local stocking rates as prescribed by the agricultural extension officer in your area.
  • Avoid grazing a wetland for two years following a fire to allow for the regeneration of vegetation.
  • Avoid overgrazing during dry summer months as this can mean insufficient plant cover for the following wet season and increase the risk of erosion.
  • Avoid footpath trampling by livestock.

Fire management

In terms of the National Veld and Forest Act (Act 101 of 1998), landowners are responsible for the prevention and management of all fires that occur on their land. Every property must have a system of fire breaks. These must be on the boundary of the property unless an exemption has been granted by the Minister or an agreement reached with the adjoining landowner that the firebreak be located elsewhere within a Fire Protection Association (FPA).

What can I do to help?

  • Avoid burning areas surrounding wetlands, which can impair functioning.
  • Avoid grazing a wetland for two years following a fire to allow for the regeneration of vegetation; and join your local FPA.

Soil erosion

Soil erosion, often caused by the diversion of water through canals and furrows, leads to the loss of the fertile topsoil layer and the depletion of oxygen in water, which harms the aquatic environment. Soil erosion can be reduced by controlling the numbers of animals, and the times they are allowed to graze.

What can I do to help?

  • Protect your wetland’s integrity and health to ensure effective delivery of ecosystem services, such as improved water quality and quantity, erosion control and flood attenuation.

Climate change

It is essential to implement effective management practices in order to combat the potentially harmful effects of climate change on the environment. Apart from changes in temperature, rainfall and ground water recharge, climate change also has an impact on the populations, ranges, migration patterns and seasonal and reproductive behaviour of animals and birds. These effects are likely to become more apparent and extensive as the climate continues to change.

What can I do to help?

  • Familiarise yourself with the concept of climate change.
  • Start discussions on possible impact of climate change with your local agricultural industry representatives and farmers associations.
  • Support local climate-change initiatives.

Alien invasive species

Fish species

One of the biggest problems associated with the introduction of alien fish species to an environment is the fact that they have no natural enemies and breed unchecked. This poses a huge threat to indigenous species because of limited food supplies, predation and changes to the habitat.

What can I do to help?

  • Familiarise yourself with the species in your wetland.
  • Do not move fish between water systems
  • Help educate the local community about the negative impact of alien fish.
  • Support efforts to remove alien fish.

Vegetation

In terms of the Conservation of Agricultural Resources Act (Act 43 of 1983) landowners are obliged to clear their land of listed invasive alien plants. They have a negative impact on biodiversity because they use significantly more water than indigenous vegetation; they represent a modification or loss of natural habitat; and alien vegetation burns at much higher temperatures than indigenous vegetation, posing a greater danger to wildlife, humans and soil structure during veld fires.

What can I do to help?

  • Be aware that controlling alien vegetation is a long-term strategy.
  • Identify the distribution of alien species in your area.
  • Clear upstream areas, and those that are more lightly infested, first.
  • Collaborate with neighbours to implement a wider strategy.
  • Monitor and record all actions for follow-up purposes.
  • Continue follow-up actions if clearing alien vegetation has taken place on your property.

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