Canterbury wetland threats

Since European settlement in Canterbury, 90 per cent of our freshwater and natural wetlands and half of our coastal wetlands have been lost through human impact.

From the mid-19th century, wetlands across New Zealand were drained for urban and rural development. While we now recognise their values and how vital they are to maintaining waterways and biological riches, our remaining wetlands continue to be threatened by human activities and invasive pest species.

Most of Canterbury’s remaining wetlands are coastal or in the foothills, high country, or margins of rivers. The small number of wetlands left contain an abundance of life that needs our collective effort to restore and protect.

Threats to wetlands



Drainage of wetlands for urban and rural development has been the primary driver of wetland loss since the mid-19th century in Canterbury and across New Zealand.

Drainage upstream, through activities like damming, can also affect crucial water sources for wetlands and cause a drop in water levels.

Rangitata river works1

River engineering and flood protection

River engineering works have historically been a major driver of wetland loss across the Canterbury Plains and coast, as they constrain rivers and coastal wetlands, disrupting natural patterns of water movement and the processes that create and sustain floodplain and coastal wetland systems.

In the past, river engineering and flood protection works mostly involved conventional engineering measures like stopbanks and groynes to control flooding, which reduced the extent and health of wetlands and other natural river processes. Along with councils from across New Zealand and around the world, we're transitioning to a more holistic approach using nature-based solutions to complement engineering works through our regionwide planting and berm transition.

Spartina weed

Plant and animal pests

Introduced plant and animal species can establish in wetlands, threatening or displacing native species. They create competition for nutrients and space, prey on native animals and eggs, and change the quality of water by stirring up sediment.

Common introduced animal species that threaten wetland environments include domestic stock, deer and pigs. Introduced predators such as cats, mustelids and rats prey on native wetland animals.

Plant species that pose a threat to our wetlands include egeria, purple loosestrife, willow and spartina.

The Canterbury Regional Pest Management Plan is a key component of our biosecurity programme and provides the regulatory requirements for priority pests across our region.

Photo: Spartina weed


Stock access to wetlands has a significant impact on the health and ecosystem of these spaces.

The nutrient levels of wetlands can increase through stock animal urine and dung, which can impact water quality. While some wetlands have the ability to absorb and filter a small degree of nutrient enrichments, at high levels excess nutrients create an environment that is toxic for plant and animal life and can destroy wetland ecosystems. Many wetlands, such as bogs and fens, are naturally low-nutrient systems and as such are highly susceptible to damage from farming practices. 

Stock can also disturb wildlife, trample plants, erode soil, and spread pest plants through seeds in their coats or hooves.

Wetlands can also be dangerous environments for stock animals, as they can become stuck or trapped in soft soils.

There are rules in place, under the Essential Freshwater Package, that restrict stock access to wetlands for these reasons.

Photo: Stock grazing near a waterbody
Pollution in Washdyke lagoon


Chemicals, such as fertiliser, can appear in wetlands through run-off, flooding or through stormwater systems.

An excess of nutrients can affect the balance of the wetland ecosystem and have a serious knock-on effect for the plants and animals that live in these spaces. Negative effects can include toxic water levels and inhibiting the growth of plants.

Photo: Washdyke Waitarakao Lagoon 


Recreation Te Waihora


While wetlands can be fantastic places for recreation, careless practices can disturb plant and wildlife and damage the physical environment.

Consideration must always be taken when jet skiing, hunting, kayaking, boating, horse riding, biking, fishing, white baiting or even walking around wetlands.

Photo: Fishing Te Waihora / Lake Ellesmere