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No.14 2007

3 July 2007

Special Issue - Effects of land-based activities on the coastal environment

Death of a thousand cuts - ecosystem disturbance

Of mud, mangroves, and radioisotopes

What risk to human health?

Rivers: the land-coast connection

Death of a thousand cuts - ecosystem disturbance

Death of a thousand cuts - ecosystem disturbance

Intertidal flats of Mahurangi Harbour. (Photo: Jane Halliday, NIWA)

‘The problem that resource managers face in trying to protect coastal environments is that damage is like death of a thousand cuts – it is often the result of many different small disturbances, the effects of which accumulate over time.’ So says NIWA scientist Simon Thrush, who is leading a long-term project on ecological disturbance modelling at NIWA.
Most environmental threats come in the form of some sort of disturbance to natural ecosystems.

Special Issue - Effects of land-based activities on the coastal environment

Special Issue – Effects of land-based activities on the coastal environment
New Zealand’s coastline is increasingly affected by land-based activities, particularly intensified agriculture and nitrate runoff, sewage disposal, coastal subdivision and sediment runoff, and heavy metal and contaminate runoff from urban centres into estuaries. Such issues are the focus of increasing and better environmental management practice.

Of mud, mangroves, and radioisotopes

Of mud, mangroves, and radioisotopes

Mangroves advancing in the Firth of Thames. (Photo: Andrew Swales, NIWA)

Many of New Zealand’s estuaries are becoming muddier, as sediment washes into them from rivers and stormwater drains and accumulates, rather than being dispersed by tides. Mangrove swamps are a feature of some of our muddy estuaries, and the Firth of Thames is a good example of a place where mangroves and mud are steadily accumulating.

What risk to human health?

What risk to human health?

Sequence of calculations to model health risks at a beach, either from swimming or from consumption of raw shellfish.

One of the direct consequences of land-based activities on the coast is the discharge of treated sewage into the sea. Pathogens (bacteria, protozoa, and viruses) in sewage can pose a risk to human health, through people swimming in polluted areas or eating contaminated shellfish.

Rivers: the land-coast connection

Rivers: the land-coast connection

Gravel extraction, Waimakariri River, Canterbury. (Photo: above, Graham Fenwick, NIWA)

(Photo: above, Alistair McKerchar, NIWA)

NIWA scientists are developing models to predict the impact of changes in river sediment loads on coastal erosion. Rivers are a key connection between the land and the sea, carrying sand, gravel, and cobbles down river, and depositing them at the coast. This material is then redistributed and groundup by waves and currents.

Research subject: Oceans