• Professor Dory Reeves is in the school of architecture and planning at the University of Auckland. The State of New Zealand Report can be found online.

In the early 1800s less than 5 per cent of the world's population lived in cities. Fast forward 150 to the 1950s and that number increased to a third. This year over half of all humans live in urban areas, with the figure predicted to be 70 per cent by 2050.

As the world's population becomes more urban our cities are increasingly coming under pressure to sustainably accommodate everyone. This phenomenon is particularly evident in Auckland where the population is expected to reach two million within 20 years.

Late last year the United Nations held a global conference in Ecuador on housing and sustainable urban development called Habitat III to address these issues. The aim was to report on the world's progress since the Habitat II conference 20 years prior, and to set out a fresh road map for future.

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At the conference's conclusion a document called the New Urban Agenda was adopted as a global framework for achieving sustainable urbanisation, including key target dates.

New Zealand did not send an official representative to Habitat III despite being a member state and signing the UN resolution in support of the conference. Nor did it produce an official report.

Because of this omission a group of researchers and academics from across New Zealand compiled a document called the State of New Zealand to benchmark where we sat in relation to the rest of the world in areas such as urban planning, our economy, access to housing and safe drinking water.

I attended Habitat III alongside 30,000 delegates from 167 countries, and at the same time, the State of New Zealand report was released.

One area the report looks at is the impact of our rapidly changing urban demographics. This is partially shaped by immigration with New Zealand's inflow of temporary and permanent residents at an all-time high.

Arrivals reached 124,000 last year, a record net gain of 67,400, making our immigrant arrivals the highest in the OECD per capita. Currently over half of all new arrivals to New Zealand choose to settle in Auckland, adding pressure to the city's struggling infrastructure.

The diversity of new arrivals - the net gains were highest for India, China, the Philippines and the UK in that order - also highlights the need for policies to ensure that new arrivals understand the cultural history and significance of Maori.

We all know housing in Auckland is expensive, but did you know it is now rated as severely unaffordable and that we are placed 347th out of 360 in an international survey of housing affordability.

While New Zealand does not suffer from slums as commonly understood internationally, relative deprivation does exist already, resulting in extremely poor housing conditions for many.

This impacts particularly heavily on Māori and Pacific Island children with high numbers of Pasifika families (43 per cent) and Māori (23 per cent) living in overcrowded homes with unfavourable consequences on child health, education and general wellbeing.

What about the rest the country? Unfortunately Auckland's urban growth is also being negatively felt there. Many outer regions are experiencing population decline resulting in the closure of small town facilities and services.

Yet there is no explicit central government policy on urban growth rates or uneven regional population growth.

New Zealand also faces some urgent sustainability challenges - 5200 people in Havelock North fell ill as a result of contaminated water last year - and the percentage of our urban population who have access to safe drinking water has dropped to just 79 per cent. Surely as a nation we should be debating these fundamental issues.

Otherwise we run the risk of degrading our social fabric by creating greater inequality - think more families living in cars as a new norm - alongside problems like increased environmental pollution.

As a planner who is also training future professionals to be good global citizens, I want to see New Zealand, as a UN member state, engage with New Urban Agenda. And we can. In 2018 the World Urban Forum will meet in Malaysia and UN member states will report back on their progress.

While New Urban Agenda is non-binding, and intended as a framework for countries to measure themselves against, I believe we must urgently debate these issues before it's too late.