Climate explained: is New Zealand losing or gaining native forests?


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Sebastian Leuzinger, Auckland University of Technology


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In recent decades, has New Zealand lost forest (both native and exotic) or gained it, courtesy of the One Billion Trees programme? What about natural habitats like wetlands?

Apart from wetlands, land above the treeline, coastal dunes and a few other exceptions, New Zealand was once covered in forests from Cape Reinga to Bluff.

So was Europe, which basically consisted of a single forest from Sicily in southern Italy to the North Cape in Norway, before human intervention.

But since people arrived in New Zealand some 850 years ago, about three quarters of the country’s native forest area has been lost. About half of the loss happened before Europeans arrived, mostly through burning to clear large areas of native bush.

Most of New Zealand was once covered in native forest.
Shutterstock/Latitude Creative

In recent decades, the loss of native forest has slowed down. For example, in the first decade of the 21st century, we lost roughly 16,000 hectares of native forest, which translates to a loss of about 0.2% of the remaining total area covered in native forest (about 7.5 million hectares). The error associated with such estimates is considerable, though, because land cover is complex and highly fragmented.




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A billion trees

According to Global Forest Watch, the drivers behind the more recent losses of native forests include exotic plantation forests, urban developments and wildfires. Indeed, the total land area dedicated to exotic plantation forests increased by about 200,000 hectares per decade between 1990 and 2017.

Commercial plantations of exotic pines have replaces native forests.
Shutterstock/Cloudia Spinner

So what has the One Billion Trees Programme achieved in comparison to these changes?

The project’s aim is to double the current planting rate and plant one billion trees between 2018 and 2028. The latest report shows about a quarter of this goal has been achieved in terms of the number of trees planted. In regards to forest area, 25,557 hectares have been reforested, about half of it with natives.

This is a remarkable achievement in light of the losses cited above and the short duration of the programme.

About a quarter of a billion trees have been planted so far, half of it native species.
Shutterstock/Kira Volkov

Saving remaining peat bogs

We think of forests as our guardians of carbon — and indeed, an aged New Zealand forest can hold about 350 tonnes of carbon per hectare. But intact peat bogs, such as the Kopuatai dome in the Waikato region, can hold up to 1,400 tonnes of carbon per hectare.

But peat bogs only store carbon if they remain wet. Once drained, they begin to emit carbon dioxide. Almost half of New Zealand’s peatlands are in the Waikato, but of a total of 89,000 hectares only 19,400 hectares remain in a natural state.

Aerial view of the Kopuatai bog.
The Kopuatai dome is New Zealand’s largest intact peat bog.
Georgie Glover-Clark, CC BY-SA

The Kopuatai bog itself is surrounded by dairy farms operating on drained peat. Collectively, the Waikato’s drained peatlands produce 10-33 tonnes of CO₂-equivalent emissions per hectare each year.

The draining of peatlands in the Waikato region did far more damage, in terms of carbon emissions, than a small loss of forest area.




Read more:
Peat bogs: restoring them could slow climate change – and revive a forgotten world


But nevertheless, planting trees and increasing our forest area is an important and necessary contribution to climate mitigation, and often comes with a myriad of other benefits, far beyond carbon sequestration.

Sometimes it’s as easy as planting your own fruit trees around your house. They will capture carbon for years to come, and keep you from buying fruit that has been transported thousands of kilometres.

They might even motivate you to reduce food waste. Globally, about 25-30% of food goes to waste. If we reduced food waste, we could save agricultural land multiple times the size of New Zealand and plant trees there instead.The Conversation

Sebastian Leuzinger, Professor, Auckland University of Technology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Most native bird species are losing their homes, even the ones you see every day



Eastern-yellow robin. Some 60 per cent of the native birds of south-east mainland Australia have lost more than half of their natural habitat.
Graham Winterflood/Wikimedia Commons

Jeremy Simmonds, The University of Queensland; Alvaro Salazar, The University of Queensland; James Watson, The University of Queensland, and Martine Maron, The University of Queensland

Across parts of Australia, vast areas of native vegetation have been cleared and replaced by our cities, farms and infrastructure. When native vegetation is removed, the habitat and resources that it provides for native wildlife are invariably lost.

Our environmental laws and most conservation efforts tend to focus on what this loss means for species that are threatened with extinction. This emphasis is understandable – the loss of the last individual of a species is profoundly sad and can be ecologically devastating.




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But what about the numerous other species also affected by habitat loss, that have not yet become rare enough to be listed as endangered? These animals and plants — variously described as “common” or of “least concern” — are having their habitat chipped away. This loss usually escapes our attention.

These common species have intrinsic ecological value. But they also provide important opportunities for people to connect with nature – experiences that are under threat.

A chain used for land clearing is dragged over a pile of burning wood at a Queensland property.
Dan Peled/AAP

The “loss index”: tracking the destruction

We developed a measure called the loss index to communicate how habitat loss affects multiple Australian bird species. Our measure showed that across Victoria, and into South Australia and New South Wales, more than 60% of 262 native birds have each lost more than half of their original natural habitat. The vast majority of these species are not formally recognised as being threatened with extinction.

It is a similar story in the Brigalow Belt of central New South Wales and Queensland. The picture is brighter in the northern savannas across the top of Australia, where large tracts of native vegetation remain – notwithstanding pervasive threats such as inappropriate fire regimes.




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Fixing Australia’s extinction crisis means thinking bigger than individual species


We also found that in some areas, such as Southeast Queensland and the Wet Tropics region of north Queensland, the removal of a single hectare of forest habitat can affect up to 180 different species. In other words, small amounts of loss can affect large numbers of (mostly common) species.

Our index allowed us to compare how different groups of birds are impacted by habitat loss. Australia’s iconic parrots have been hit hard by habitat loss, because many of these birds occur in the places where we live and grow our food. Birds of prey such as eagles and owls have, as a group, been less affected. This is because many of these birds occur widely across Australia’s less developed arid interior.

This map shows the number of bird species affected by habitat loss in any region. Grey zones indicate parts of Australia where habitat loss has not occurred. Blue zones have up to 90 species affected by habitat loss, yellow is up to 120 species affected, while the highest category, red, is up to 187 species affected.
Conservation Biology

Habitat loss means far fewer birds

Our study shows many species have lost lots of habitat in certain parts of Australia. We know habitat loss is a major driver of population declines and freefalling numbers of animals globally. A measure of vertebrate population trends — the Living Planet Index — reveals that populations of more than 4,000 vertebrate species around the world are on average less than half of what they were in 1970.

In Australia, the trend is no different. Populations of our threatened birds declined by an average of 52% between 1985 and 2015. Alarmingly, populations for many common Australian birds are also trending downwards, and habitat loss is a major cause. Along Australia’s heavily populated east coast, population declines have been noted for many common species including rainbow bee-eater, double-barred finch, and pale-headed rosella.

Decling common species – rainbow bee-eater (left); double-barred finch (top right); pale-headed rosella (bottom right)
Jim Bendon, G. Winterflood, Aviceda



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This is a major problem for ecosystem health. Common species tend to be more numerous and so perform many roles that we depend on. Our parrots, pigeons, honeyeaters, robins, and many others help pollinate flowers, spread seeds, and keep pest insects in check. In both Europe and Australia, declines in common species have been linked to a reduction in the provision of these vital ecosystem services.

Common species are also the ones that we most associate with. Because they are more abundant and familiar, these animals provide important opportunities for people to connect with nature. Think of the simple pleasure of seeing a colourful robin atop a rural fence post, or a vibrant parrot dashing above the treetops of a suburban creek. The decline of common species may contribute to diminished opportunities for us to interact with nature, leading to an “extinction of experience”, with associated negative implications for our health and well-being.

We mustn’t wait until it’s too late

Our study aims to put the spotlight on common species. They are crucially important, and yet the erosion of their habitat gets little focus. Conserving them now is sensible. Waiting until they have declined before we act will be costly.

These species need more formal recognition and protection in conservation and environmental regulation. For example, greater attention on common species, and the role they play in ecosystem health, should be given in the assessment of new infrastructure developments under Australia’s federal environment laws (formally known as the Environment Protection and Biodiversity Conservation Act 1999).

We should be acting now to conserve common species before they slide towards endangerment. Without dedicated attention, we risk these species declining before our eyes, without us even noticing.The Conversation

Jeremy Simmonds, Postdoctoral Research Fellow in Conservation Science, The University of Queensland; Alvaro Salazar, Postdoctoral Research Fellow, The University of Queensland; James Watson, Professor, The University of Queensland, and Martine Maron, ARC Future Fellow and Professor of Environmental Management, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.