If the entire world lived like a New Zealander we'd need more than two planets to sustain us, studies find.

We're known for being clean and green, but Kiwis are still eating up at least twice their fair share of the planet when it comes to sustainability.

Two papers released today by the Royal Society of New Zealand explore how many people the country could support sustainably - and how comfortably.

They found that if the entire world was to live like a New Zealander, we would require more than two planets to sustain us.

Some estimates had put the number as high as five.


The research looked at specific areas - climate change, food production, water quality, native biodiversity, transport and fisheries - where sustainability became an issue and could constrain the country's ability to provide wellbeing to its residents.

The reports are: The Sustainable Carrying Capacity of New Zealand and Constraints to New Zealand's Sustainable Well-Being.

The society's chief executive, Dr Di McCarthy, said the papers offered a strategy on how to operate within the constraints of our resources.

And despite the popular view, the papers found that achieving sustainability was not as simple as a trade-off between our environment and economy.

"Instead, the relationships are complex and interwoven."

She gave an example of the various uses of a river.

Where raft companies, kayakers, anglers, iwi, environmental groups and farmers might want different flow levels, sustainable management of the river would have to take all views into account.

Landcare Research's portfolio leader of governance and policy, Dr Suzie Greenhalgh, who is speaking at the papers' launch in Wellington today, said any responses to constraints over natural resources had to recognise the many connections between the economy and the environment.

New Zealand's lakes, rivers and streams had been affected by increases in pastoral agriculture, which had resulted in a seven-fold increase in the use of nitrogenous fertiliser over the past 20 years and irrigation water takes that had reached or exceeded limits.

But shifting dairying off leaching-prone land and on to more suitable terrain could reduce overall nitrogen pollution without reducing overall output and farm profitability.

Despite options for better performance, New Zealand's progress towards better use of its resources - capable of producing enough calories for 20 million people and enough protein for 45 million people - was slow in many cases.

And while a growth in our economy of 68 per cent within the past two decades had brought about only a 20 per cent increase in greenhouse gas emissions, not enough was being done to halt the growth of our overall greenhouse gas emissions.

This was despite extensive potential supplies of renewable energy.

Study contributor Dr Mike Joy, a senior lecturer at Massey University's Environmental Science and Ecology Group, told the Herald that discussions on sustainability were "long overdue".

"The message is simple - there is no free lunch, at least not the banquet we are having now. Our natural advantages, water and soil, will sustain us but we must not jeopardise them any further."

Sustainability Council executive director Simon Terry said not being sustainable would load costs onto future generations and "risk systems breaking down".

Footprint out of kilter

• "Fair earth shares" are referenced when measuring an "ecological footprint".

• The "fair earth share" footprint is worked out by taking the world's total amount of arable land globally and dividing it by the world population.

• While the current "fair share" is 1.7 global hectares per person, estimates for New Zealand have ranged between 5ha and 8ha. In 2010 New Zealand's ecological footprint was 4.89 global ha per person - five times that of a person in India and almost three times the "fair earth share".

Raglan tops Shore for sustainability

They might like being richer, smarter, more fashionable, influential, beautiful and higher up the career ladder - but the "North Shore" type finishes last in the sustainability stakes.

The people of Raglan and Otara top the list.

Drawing on the book 8 Tribes: The Hidden Classes of New Zealand by Chris Brown and Jill Caldwell, a study under the New Zealand Footprint Project has gauged the ecological impact of eight different Kiwi "tribes".

Tribes were defined by income and lifestyle, and labelled according to their stereotypical state of mind.

In terms of "Earth shares" - calculated by dividing the world's total amount of arable land by the world population - the North Shore tribe would need nearly four Earth planets to sustain their lifestyle, compared with a fair Earth share of one. The New Zealand average sat at just over two.

With an annual household income of $130,000 and characterised by "preferences for high levels of consumption, travel and large houses", the North Shore tribe ranked the highest of the groups in resource over-use, followed by the Remuera and Grey Lynn tribes.The best ranked tribes - Otara and Raglan, with scores of around 1.7 - were still rated worse than the global average in sustainable living.

Otago Polytechnic sustainable practice adviser and research manager Ella Lawton, who wrote the chapter, concluded the amount of money individuals earned allowed them to exercise different types of lifestyles with varying levels of consumption.

"The 8 Tribes case study shows that on average the income bracket that someone is in correlates with the size of their ecological footprint."