Our changing landscape: Growing cities, expanding mines, and dwindling native habitat

Saturday, 7 March 2020

Thousands of hectares of native habitat have been razed in recent years to make way for mines and paddocks, new data shows.

The extent of native habitat loss New Zealand-wide is equivalent to around 12,000 rugby fields, or an area roughly the size of Wellington city.

Pokeno, south of Auckland, betwen 2012 and 2018.

The data, released by Manaaki Whenua/Landcare Research, shows land use changes nationwide between 2012 and 2018. It is the first major update of the database, which has been maintained since 1996, in seven years.

It shows how and where 33 classes of land type – from urban settlement, to mines, to indigenous forest, to wetlands – have changed in expanse.

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An analysis by environmental organisation Forest & Bird shows a considerable loss of native habitat during that period, often at the expense of farmland, forestry and mining.

Across the 13 land types deemed to be native habitat, 12 of them reduced in extent, while one increased: Combined, it amounted to a collective loss of 12,388ha.

It contrasts with increases in human-influenced land types: Productive grasslands (primarily farmland) increased by about 23,000ha, urban areas by 6000ha, and mines and dumps by 2000ha.

Cross-referencing the data to satellite imagery shows much of the native habitat loss happened on private land, and was not systematic; it was a consequence of many hundreds of landowners making sometimes minor changes on their land.

Ranking all 33 land classes by how their footprint changed shows native habitats dominate the lower end; All but two are in the bottom half, and only one makes it into the top 10.

The land types that expanded the most include mines and dumps, harvested forests, transport infrastructure and urban areas.

It bolsters concerns held by Forest & Bird that native habitat is not adequately protected on private land.

'Currently, the level of support given to landowners to identify and protect their important natural areas depends on their regional council's willingness to do so,' said the group's chief executive, Kevin Hague.

'While many landowners are doing the right thing and protecting the special places in their trust with little support, there are also those who have destroyed these areas when there is a business case to do so.'

He supported the draft National Policy Statement on Indigenous Biodiversity, currently open for consultation, which would require councils to find and protect significant areas of biodiversity on both public and private land.

'After years of failure to put in place a Policy Statement to guide how we should provide for native animals and plants, it's time for land owners, farmers, and councils to put nature first, and make sure that our native species have somewhere to call home,' Hague said. 'It was theirs long before it was ours.'

The intent of the plan has been supported, in principle, by farming groups; Federated Farmers released a joint statement with Forest & Bird in November supporting the process.

Concerns remain, however, that the requirements could be too onerous, and may not recognise the voluntary work done by the farmers who have protected native habitat on their land.

FOREST TO MINES

Among the most significant findings in the data was the loss of indigenous forest, among the most important types of biodiversity, in part because it is difficult to replace.

Nationally, 2300ha of indigenous forest has been removed since 2012 – roughly the same amount of land area Auckland city expanded by over the same period. More than half of the indigenous forest loss happened on the West Coast.

Although the region has the most indigenous forest to begin with, it also removed the most of all regions when ranked proportionally.

Particularly noteworthy is what replaced the indigenous forest: In many cases on the West Coast, it was a mine.

The data shows nearly 400ha of mining land replaced indigenous forest, and the footprint of mining as a whole expanded significantly.

Despite the industry's sudden economic contraction in recent years, its physical footprint has grown by about 45 per cent nationally since 2012. The most common type of land to be displaced by mining on the West Coast was indigenous forest.

Mines and dumps – which are a combined category – now make up significantly more of the West Coast's land area than urban areas, and its growth on the West Coast pushed mining to have the second-largest proportional increase of land classes nationally.

While indigenous forest had a modest reduction nationwide, manuka and kanuka forest had a far bigger loss in footprint.

Together, they contracted by around 15,000ha nationally, predominantly replaced by farmland and exotic forest.

This was most evident in Manawatu-Whanganui and Gisborne, which each lost between four and five per cent of its respective manuka/kanuka forest.

It was partly made up for by an expansion of broadleaved indigenous hardwoods – typically scrub that eventually makes way for indigenous forest – which was the only native habitat land class to grow, which it did by more than 10,000ha.

Not all native habitat loss could be linked to human activity, and in some cases, the loss was minor.

An important native habitat type, sub-alpine shrubland, had minor losses, most of which were due to landslides. Landslides took out indigenous forest too, but it was far outweighed by the amount removed deliberately by humans.

Another sensitive native habitat that remained largely the same was alpine grasses, with a minor 15ha loss to manuka/kanuka forest.

A more concerning change is the loss of 2500ha of grey scrub, reflecting more than 2 per cent of its national land area. Grey scrub is typically matagouri, and can be an important habitat for small species such as moths, lizards, beetles and other insects.

More than half of this loss was in Canterbury, and nearly all of the displaced grey scrub was turned to farmland.

Another potentially problematic decline was in herbaceous freshwater environments, which are usually wetlands. It had a net loss of about 1000ha, driven mostly by declines in Southland and the West Coast.

Although in many cases it was native habitat being reduced, the land class that reduced the most was gorse and broom, which declined nearly 5 per cent nationally.

GROWING CITIES

As the footprint of other land types has either slowed in growth or declined, cities are continuing to expand.

They have grown a collective 6000ha since 2012, an expansion of more than three per cent, the data shows.

In net terms, Auckland has grown the most, accounting for more than one-third of all urban expansion. Proportionally, however, it was surpassed by both Tasman and Bay of Plenty, each of which expanded by around six per cent, to Auckland's five.

A small number of regions had little to no urban growth: Gisborne had none, and Hawke's Bay, Northland, and the West Coast each grew less than 1 per cent.

By far the largest source of new urban land was high producing farmland; although that also grew overall since 2012, it was in spite of losing more than 5000ha to urban development.

In a smaller number of cases, urban land was built on crops or orchards, particularly in Auckland.

The possible loss of horticultural land south of Auckland has been a growing concern, and the data shows it declined nearly 200ha, almost all to urban development.

The footprint of transport infrastructure – in this case meaning arterial roads rail yards, and airport runways – also grew considerable. It was heavily concentrated in Wellington and Auckland, while several regions had a net loss of transport infrastructure, including Gisborne and Waikato.

Urban parks also increased, but predominantly due to a vast increase in Canterbury, as a consequence of red-zoning after the earthquakes. Only a handful of regions had a more than one per cent increase in urban park area, including Taranaki, Manawatu-Whanganui and Auckland.

An interactive map showing the changes can be viewed here.