We think of Paris as a romantic, antique city anchored to its past - but the French capital is proving itself a shining example of modern ways to fight climate change and become more resilient. So what can our City of Sails learn from the City of Light to make itself greener? In the first of a four-part series, science reporter Jamie Morton looks at the "eco-district".
It's a muggy late-spring afternoon in Martin Luther King Park, a rare haven of lush greenery amid the high and packed cityscape of Paris.
The Louvre, Notre Dame Cathedral and most of the city's other famous landmarks are a 15-minute taxi ride away, but this patch of Paris isn't the same scene we see on travel shows.
Here in the 17th district, it's not so much charming cafes and rich classicism but rail yards, cranes, concrete apartment blocks and tobacco shops with graffiti-covered roller shutters.
This 10ha parkland at its heart also isn't the storybook Paris of statues and fountains but what might appear scruffy, overgrown and wasted space on first impression.
You'll find brambles, wet ditches, water plants sprouting out of ponds - even the lawns look scraggly and overdue a mow.
The average tourist won't realise they're standing in a perfect blueprint for sustainable urban design.
Its biotope pond is a rare thing in Paris and supports a rich ecosystem of more than 500 plants, insects and amphibians.
The dead leaves of the surrounding tilla trees make for better compost; nearly half of its watering needs is met by rainwater that is itself collected and channelled toward wetlands.
It's been carefully crafted not just to sap air pollution, but to act as a giant air conditioner, thanks to the shade of its trees and the natural phenomenon of evapotranspiration - cooling the ambient air with water vapour - that's generated by the greenery.
The park itself is the linchpin of the Clichy-Batignolles project that surrounds it.
This takes in around 3400 housing units and 140,000sq m of office space, much of it being built to accommodate around 7500 residents and 12,700 jobs in the coming years.
Its architects have squeezed out of its design every potential greenhouse gas emission they can.
Energy consumption in buildings has been strictly limited to fall below current city energy regulations, and all have been connected to a heating grid supplied with geothermal energy.
Rooftops would be equipped with a total 35,000 sq m of solar panels, generating around 3500 MWh each year, while a further 16,000sq m of roof space would be planted with more greenery.
Nearly all household waste is automatically collected using the city's first underground pneumatic network: no wheelie bins, no rubbish trucks.
Shops, schools and recreational facilities have been created in the ground floor of the buildings to create a dense, diverse community, where its residents - half of them accommodated in social housing - will have most of what they need at hand.
If they do need to travel, it won't be by vehicle - individual cars are discouraged and parking is severely limited - but by five major public transport hubs a short walk away.
Clichy-Batignolles, now just three years away from completion, is what's called an eco-district.
Paris architect Catherine Haas saw a case for thousands more of these ultra-sustainable neighbourhoods across the planet - including Auckland.
"I believe it is an example of dense, high quality, mixed usage and sustainable city planning for all dense cities of the future," she told the Herald.
It's a huge challenge for the planet: a new report showed that much of mankind's battle against climate change would have to be won in the next three years.
The planet's large cities contribute around three quarters of carbon emissions, and making buildings and infrastructure greener is seen as a big area in putting the globe on a safer trajectory.
Paris, population 11.9 million, has decided to take the lead with bold and immediate action.
The city wants to cut back emissions from road traffic by 20 per cent by 2020, put a major dent in its air pollution levels and drive district heating powered by renewable and recovered energies.
By 2050, Paris aims to be producing 75 per cent fewer greenhouse gas emissions it was in 2004.
It's a big ask for one of the densest cities in the world: the inner ring of Paris is home to around 2.2 million people, crammed into an area that equates to around 3700 people per sq km.
Its core is characterised by those tight rows of six-storey, Haussmann-style apartment buildings that look pretty in films, but are tough to extract green gains from.
But Paris has the brave leadership of mayor Anne Hidalgo, the new chair of the C40 Cities - a global climate-focused collective of 89 centres, including Auckland - who has battled to ramp down auto-dependency and reclaim public space.
The city is also now synonymous with the landmark UN climate agreement signed by nearly 200 governments, while France's new young president, Emmanuel Macron, has vowed to "make the climate great again" after US President Donald Trump pulled his country out of the deal.
As the planet warms, Paris is predicted to experience more severe heatwaves - one 2003 event directly linked to climate change killed several elderly residents - along with floods that could potentially affect around 83,000 people in the Ile-de-France region.
Auckland is in for much of the same.
According to projections, temperatures in our largest city could be several degrees warmer by 2100, by which time there could be anything between 40 and 60 extra days where maximums climb over 25C.
Ex-tropical cyclones will likely be stronger and cause more damage as a result of heavy rain and strong winds; sea levels could be up to a metre higher by 2115 and storm surges would compound the threat to Auckland's low-lying coastal areas.
When it comes to being greener, Auckland is blessed with a much more open natural environment than Paris.
Its urban density only stands at 24.9 people per hectare, many areas of high biodiversity are still intact and air quality is good compared to other major cities.
Yet these advantages didn't make its path to sustainability any easier.
A recent report showed the city didn't have a public transport system suited to a low-density city and wasn't doing enough to adapt to a world where we pay more for energy, waste, water and greenhouse gas emissions.
It showed businesses weren't being encouraged to think how their consumers value sustainability.
Against these constraints, Auckland has set itself a target of slashing greenhouse gas emissions by 40 per cent by 2040 and reducing the amount of waste going to landfill to nothing.
Auckland Council has tried to get the city heading in this direction through such ways as organic waste trials collecting food scraps, paper towels and tea bags and turning them into compost.
But can we boast anything as radical as Clichy-Batignolles?
Our closest example might be the Wynyard Quarter, a 37ha, mixed use downtown development bordered on three sides by the Waitemata Harbour.
Once complete in 2030, the precinct will be home to around 3000 residents and 25,000 workers, with the first of 500 to 600 new apartments, town houses and duplexes due to be complete next year.
Panuku Development's goals are similarly lofty to Clichy-Batignolles and include big cuts on the status quo in stationary energy greenhouse gas emissions.
This means less grid electricity consumption, peak electricity demand, stormwater discharge and private vehicle travel - and ultimately fewer household operating costs.
All of it would be achieved by measures like high energy efficiency, clever use of renewables, passive design, stormwater treatment, landscaping, smart-metering and encouraging shared transport and biking over cars.
The precinct is also the first large-scale development of its type in New Zealand to target the 7 Homestar environmental rating.
Auckland Council and a group of businesses are now working on a precinct-scale development at Auckland Airport.
Auckland Council chief sustainability officer John Mauro said model eco-districts like Clichy-Batignolles could show us how to combine every element of sustainability in a single area.
"And then, of course, it's about replication and scaling up."
Using new technology to design smarter communities wouldn't save us, but it would offer some exciting new ways to move further and faster, he said.
"I think Auckland's challenge, with our 2040 goal of 40 per cent overall emissions reduction, is that it's an overall target not per capita.
"So we need to start thinking of every new build and every retrofit as a zero carbon challenge."
Was it fair to compare our city with Paris?
Mauro thought making a contrast was tricky.
Auckland today struggled with a historic underinvestment in infrastructure, causing problems for everything from water quality and quantity to pressures on community cohesion.
Paris was somewhat unique, with very strict planning to maintain culture and heritage, so didn't have the same approach to intensification as Auckland, a newer city with arguably more agility to drive harder.
Yet it was Auckland's extraordinary growth that was also a major weakness.
Sprawling development simply wasn't financially, socially or environmentally smart or sustainable.
Depending on how one saw it, all of that land that Auckland hadn't yet swallowed up could be an advantage or a disadvantage, Mauro said.
"While the cultural and political context is quite different, the physical limits to a city like Singapore has spurred major innovation and big leaps forward.
"So having land available allows us to be a bit lazy and be led by the nose by those with vested interests in land banking and profit that might not be in the best interest of the city and citizens."
Yet, on the other hand, that undeveloped land - and our water access - was an asset in itself, as well as a value proposition to attract and retain talent and population base.
"As an immigrant, I can't really speak to the Aucklander mindset - but I can reflect that nearly 40 per cent of us weren't even born in New Zealand," he said.
"So we bring our own mindsets to this city - and I think given the advances in cities around the world in this area, it's helping to colour our collective mindset quite a bit greener."
What is sustainability?
Sustainability typically involves the relationship between ourselves and our planet - and how we can reduce our impact on the environment so that we can carry on existing.
It often also involves making our economies and communities more resilient to change.
Currently, the planet is demanding more from nature than it can generate for us - and our populations use the equivalent of 1.6 planets to provide the resources we use and absorb our waste.
Human activity is also threatening our sustainability through climate change, which, if left unchecked, will mean major impacts for every aspect of our lives.
Tale of two cities
Today: Making Auckland green again
Tomorrow: Building greener
Thursday: Moving greener
Friday: Boosting our greenery
• Jamie Morton was hosted in Paris by the French government