Meltdown of a dryland landscape



Many people have taken the opportunity to look at their own backyard because overseas travel is currently not possible.

Travellers who had not been through the Mackenzie Basin for a while are surprised to see the extent of green landscapes, which they remembered as a golden colour.

Increasingly, vast tussock grasslands, which evolved over a long period since the ice disappeared, are being squeezed out by irrigation. As a result, many of these locally endemic flora and fauna species are being threatened, at risk, or vulnerable, some may have already gone extinct.

The absence of predatory land mammals provided a kingdom for birds and lizards for a considerable time until exotic mammals were introduced.

Author and conservationist Tim Flannery considers the ground nesting birds having evolved to become the New Zealand ecological equivalent of giraffes, kangaroos and tigers native to other countries.

Yet this ecological importance does not seem to be recognised nor valued enough. Endemic plants and animals of the Mackenzie Basin are incredibly robust considering their ability to cope with minus temperatures in double figures during the winter, and drought conditions during the summer.

These attributes of adaptation are unique on a global scale. Peppercress Lepidium solandri) is just one of many special plants. Its current conservation status is threatened

Although its habitat is versatile, fewer than 1000 plants are known in the wild and very few sites are protected. While animal browsing and weed competition will affect the species, by far the biggest threat is land use intensification.

Non-migratory galaxiid species present in the basin are the most threatened fish. They evolved into distinct species and live in the stream or river where they hatched.

They do not migrate, as they have been isolated for a long time. Water abstraction, increasing deposits of sediments and reduction of suitable habitat for spawning are serious effects on these freshwater species.

In reality, not many species can survive in a fragmented landscape. Natural areas become islands among green pastures. Irrigating pastures and crops adjacent to dry, low fertility ecosystems has significant impact, especially at the edges of the dryland. Nutrient run-off paves the way for aggressive pasture grasses to invade and take over, thus reducing natural areas.

There are other unknown effects, because little or no research has been done here, for example the effects of herbicides and insecticides on dryland ecosystems. Temperature inversion conditions may be a potential risk of spray drift.

While getting away from mono-cultures is a positive aspect of farming, some caution is needed. Some of the plant species included in regenerative farming methods may pose a potential risk and become weeds.

It is known that Russell lupins spread rapidly, and their removal from conservation areas requires considerable resources, but little is known how some other species may

Landscape and ecological values of the Mackenzie Basin need to be protected. Future generations deserve to benefit and enjoy these values.

  • Ines Stager is a landscape architect based in Geraldine, a board member of the Royal Forest & Bird Protection Society and a committee member of the local branch.

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