New Zealand cities are spreading, eating into our environment as they go

Alex Braae for The Spinoff.

A major new report on the environment delivers a grim summary of the challenges faced. Among them is the impact of growing cities, writes Alex Braae.

New Zealand's cities and towns are expanding, putting an increasing amount of pressure on both agriculture and biodiversity.

That's one of the key conclusions of the Environment Aotearoa 2019 report, which assesses the state of the nation on a range of measurements. The report took an interconnected approach, with human activity a key component in each of the nine top environmental issues.

A major theme of the report was changing patterns of land use, and the effect that was having on the ecosystem. Between 1996 and 2012, the total area of urban land in New Zealand increased by 10 percent to approximately 228,000 hectares. That was most pronounced in Auckland, followed by Waikato and Canterbury.

Of that, 29 percent of new urban areas were on "versatile" land. That means land that can be used for farming or protection of biodiversity, and is highly valuable for the economic base of the country. The changes were largely driven by population growth, which is happening faster in urban areas compared to rural areas.

As well as that, land is becoming more fragmented, as it gets increasingly picked apart for lifestyle blocks. As of 2013, 35 percent of the Auckland region's versatile land was being used for lifestyle blocks. Given land turned over to housing is more economically valuable than land kept as either agriculture or wilderness, it is unlikely that much of this land will be converted back.

The cumulative effects of these changes in land use have been significant, and complex. Among them is the fact that cities are generally located on or near the best, most productive land in the country, because historically that was a necessity. However, as the cities expand, that means they're spreading out over that land, changing it irreversibly and ending its versatility and value for either agriculture or biodiversity.

As well as that, it has contributed to changes in farming which have themselves damaged ecosystems – particularly waterways. With less highly productive land available for farming, it means the inputs (such as fertiliser) that are put into the soil to grow grass need to be more intensive. That in turn increases pollution of rural waterways. Some of the intensification of farming that is taking place is unrelated to urban expansion.

It also has an impact on biodiversity, with many unique native species of birds, plants and insects in danger of going extinct. As the amount of land available for biodiversity is cut back and fragmented, that land is less able to support ecosystems. While human activity has had an impact on biodiversity since the first arrival of Māori, the report stressed that most measures showed an increasing risk to biodiversity. The bright spots came only as a result of "intensive conservation efforts."

Hanging over the report as a whole was the increasingly visible effects of climate change. Higher likelihoods of droughts, floods and shifting seasons means that versatile land will become ever-more important for food production. Rising seas, which have been clearly documented, will also in turn affect both urban and rural areas.

The Spinoff.