Productive land loss to urban sprawl grows

WELLINGTON: A new report paints a stark picture of the environment under relentless pressure.

The Environment Ministry and Stats NZ yesterday released Our Land 2021 — a look at land use and the state of the environment in recent decades.

It is the latest in a series of environmental reports based on themes such as air, marine, freshwater and climate.

It describes the loss of productive foodgrowing land to urban sprawl, an eroded environment under pressure from more cows and increased intensification.

Only about 15% of New Zealand land is flat, with good soil and climate that makes it ideal for food production, needing less irrigation and fertilisers.

This includes places such as Pukekohe, near Auckland, and parts of the lower North Island.

Productive areas are often on the city fringes — right in the areas often where there is urban expansion.

The area of highly productive land lost to housing increased by 54% between 2002 and 2019. Market pressures will increase, with more demand as the population grows here and overseas.

Urban areas expanded by 15% from 1996 to 2018, and 83% (25,248ha) was converted from farmland.

Ministry for the Environment (MFE) departmental chief science adviser Dr Alison Collins said if productive land was not available for agriculture it forced less suitable areas to be used.

They required more fertiliser and more irrigation which could hurt the wider environment.

‘‘The worrying thing for me from the report is that it’s going to become even more difficult to make those wise decisions when you’ve got a growing population needing more housing, but also needing a food supply,’’ Dr Collins said.

‘‘And then you’ve got a changing climate as well. So you’ve got all that uncertainty to try and wrestle with, so the decisions are going to be harder to make.’’

City fringes are where there are many lifestyle blocks — the numbers of which are also increasing — removing this land from commercial food production.

Half of the total land area in New Zealand is now used for agriculture, forestry and housing.

MFE secretary for the environment Vicky Robertson said the Government was working on national policy on the tension between housing and productive land which is expected by the end of the year.

The number of dairy cows has doubled since the 1980s, rising from 3 million to almost 7 million in 2015, dropping to more than 6 million in 2019.

Irrigation has nearly doubled since 2002 — the majority in Canterbury.

Nationwide, 80% of monitoring sites failed to meet the targets for at least one soil quality indicator — and this is neither trending up or down.

Substances such as nitrogen are within the target range at nearly three quarters of sites (72%) but waterways are still being polluted with excess nitrogen.

The report says it shows the targets are not stopping the environment being damaged.

Sectors such as crop vegetable, cereals, seeds, orchards and vineyards do not have targets for nitrogen at all.

Ms Robertson said we were facing hard decisions.

‘‘It’s almost like a canary in the mine situation, where we’re seeing enough evidence of the cumulative impact of our decisions that if you project that forward, which we don’t do in the report . . . we need to find a better way of making hard decisions.’’

At present, soil quality is measured according to a list of attributes — for example the amount of a particular chemical present.

Dr Collins said a better measure might be soil health.

‘‘This is a more holistic concept of the soil’s ongoing capacity to function as a living ecosystem and sustain plant animal and human health.’’

A healthy soil supported high biodiversity which was more resilient, while intensive management stripped that biodiversity.

MFE deputy secretary strategy and stewardship Natasha Lewis said that switch was an example of the need for better environmental monitoring and reporting more generally.

‘‘It requires investment and it requires a commitment across the country in terms of how the information is collected.’’ — RNZ

❛ . . . you’ve got a growing population needing more housing, but also needing a food supply