February 2nd is World Wetlands Day, so what better time to do a feature on wetlands and the benefits they provide.
At a global scale, about 50% of the world’s original wetland area has been lost. Both in New Zealand, and around the world, remaining wetlands are under pressure from direct and indirect human impacts. In the past 150 years in New Zealand, more than 90% of wetland area has been removed (Clarkson et al. 2013). This loss rate is amongst the highest in the world and has been due to drainage, land development and land use change.
Ausseil et al. (2011) state that the South island has 16% of its original wetland area remaining, whereas the more populated and intensively developed North Island only has 4.9%. Research by Pannell et al. (2021) showed that approximately 3000 hectares of New Zealand’s remaining wetlands occur on sheep and beef farms, with 13,000 hectares occurring on dairy farms. The loss of wetlands, and the extent of what remains, signals the importance that New Zealand farming systems have in protecting and restoring these ecosystems, now and into the future.
Protecting and restoring wetlands is something that is of key importance to Sustainable Development Goal #15 – Life on Land. Under this goal there are two key targets that are of importance for wetlands:
- Target 15.1: Ensuring conservation, restoration and sustainable use of terrestrial and inland freshwater ecosystems and their services
- Target 15.5: Take urgent and significant action to reduce degradation of natural habitats, halt the loss of biodiversity, and to protect and prevent the extinction of threatened species.
These targets are really relevant to our approach to looking to protect, restore, and enhance wetlands in New Zealand and in our farming systems.
What are wetlands and what benefits do they provide?
Wetlands are where the water table is at or near the surface of the land, or where the land is permanently or temporarily (as with the tides) covered with water (DoC, n.d.). Wetlands can be freshwater or estuarine, and both are found on farms in New Zealand.
So, what benefits do wetlands provide?
1.) Water quality Improvements
Wetlands play an important role in improving water quality by purifying water. They do this by storing nutrients and pollutants in their soils and vegetation, as well as by trapping sediments. The efficiency of nutrient removal by wetlands depends on the position of a wetland within a catchment, but nitrogen and phosphorus are removed or significantly reduced by wetlands. This has a positive benefit for water downstream of these wetlands and other receiving aquatic environments.
2.) Flood control
Wetlands can reduce the impact of flooding by providing a physical barrier to slow the speed of water, and reduce the height and force of floodwaters. Wetlands are able to absorb heavy rain and release water gradually, effectively acting as natural reservoirs that can receive high volumes of rain and floodwater.
3.) Carbon storage
Sequestering carbon is another role that wetlands play in the environment. Provided that wetlands are protected, maintained and restored, wetlands are able to mitigate climate change by sequestering carbon. However, if wetlands are not maintained, they become sources of greenhouse gas emissions to the atmosphere.
4.) Biodiversity and habitat provision
Wetlands provide unique habitat for New Zealand’s plants and animals. As a result, wetlands are very biodiverse, supporting many native species. New Zealand’s remaining wetlands support a high proportion of threatened plants and animals, including 67% of freshwater and estuarine fish species, as well as 13% of nationally endangered plant species.
5.) Cultural values
Wetlands have important cultural significance for Māori. They are regarded as taonga (treasures of significant value) that are closely linked to their identity as tangata whenua (people of the land) (Clarkson et al. 2013). There is cultural and historical importance of wetlands with some wetlands having wahi tapu (sacred places), as well as wetlands supporting mahinga kai (food gathering).
6.) Recreation, tourism and education values
Wetlands also provide value to humans in the form of recreation, tourism, and education opportunities. There are many ways in which people associate with wetlands in New Zealand, and their protection and restoration ensures that these values and activities can continue to occur.
What can farmers do to protect and maintain wetlands on their farms?
Dairy NZ’s ‘Making the most of wet areas on farm – a farmers guide to restoring natural wetlands’ resource identifies key actions that farmers can take to protect and maintain natural wetlands on farm. These are to:
- Make a plan
- Keep stock out
- Keep it wet
- Control plant weeds
- Control animal pests
- Plant, if plants are needed
