Canterbury wetland threats

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.

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.

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.

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.

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.

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.