How to reduce your carbon footprint when you live in the city.

At some point during the past decade, humanity sailed across that invisible line that meant more of us now live in cities than in the countryside. For the first time in the history of civilisation, we have become a majority urban species and, if the United Nations is to be believed, this will increase to 66 per cent by 2050.

The metropolis may afford many a cultural, social and economic perk, but there’s no avoiding the fact that it can also be toxic to our health and wellbeing. In 2014, the world reacted in shock to images of Beijing residents basking under the neon glow of an LED sunrise in Tiananmen Square as a thick blanket of smog obscured the actual sky, and yet London also broke its annual pollution cap in the first five days of 2017. Paris has resorted to banning car use on alternate days during peak pollution periods, while oxygen bars are commonplace in Tokyo. One enterprising Canadian company has even started selling bottled mountain air to choking city-dwellers.

We know there’s a huge problem to tackle and, while steps such as China’s ratification of the Paris accord against climate change show a shift in the right direction, the sceptical proclamations of Trumpism threaten a swing back the other way. When governments fail us, it’s often hard to know how we can act as individuals to improve our environment. Planting trees can be impractical and carbon offsetting too abstract, so here are a few everyday, practical tips for greening Gotham.

Switching to green energy doesn’t mean strapping a solar panel to your roof. In the UK, there’s now a bevy of clean-energy operators such as Green Star, LoCO2 and OVO that offer renewable utilities at accessible prices. East London startup Bulb claims to undercut mainstream operators by about £250 a year, and offers a simple postcode calculator to work out what you could save by going green. Appealing to our wallets rather than our ethics is often the best way to enact change.

It can’t just be down to the little guy, however, which is why it’s encouraging to see corporations such as Google pledging to make its data centres and offices for 60,000 staff green by the end of this year. Denmark – ever the eco-innovator – plans to become the world’s first completely renewable country by 2050. The tide seems to be changing on a corporate, national and individual level, so bin the mini wind turbine and look into slicker green solutions.

It turns out your mum was right – eating broccoli really is good for you. Not only that, it could be transformative for the planet, too. Recent research published in the Proceedings Of The National Academy Of Sciences journal found that livestock account for 14 per cent of greenhouse gas emissions, but this could balloon to 50 per cent by 2050. Adopting a vegetarian diet would reduce these emissions by 63 per cent. There’s a powerful health incentive, too. A fully vegan diet could help avoid eight million deaths by 2050, and also save about $30tn (£800bn) annually in economic costs such as healthcare and lost labour.

Buying local has been one of the great rallying cries of the 21st century, but the concrete jungle often falls short on rolling fields of corn and verdant orchards. This is why a new breed of underground farm is cropping up, using disused railway tunnels to create energy-efficient hydroponic setups. One such operation is the imaginatively named Growing Underground, which uses 6,000sq ft of disused air raid shelters in south London to grow microgreens such as watercress, sorrel and coriander.

When it comes to transport-related pollution, there’s a clear and present danger: the car. Private vehicles account for about 70 per cent of total traffic-related CO2 emissions compared with 12 per cent for aviation and just one per cent for trains. This isn’t necessarily because these other forms of transport are far greener, however. Per passenger, they are not. It’s just that we rely on cars for too much. According to the US’s Urban Mobility Scorecard, delays due to traffic kept commuters locked in their tin cans for a staggering seven billion wasted hours in 2015.

Cycling is obviously the greenest option here, but comes with its own hazards in congested city centres, not least turning up to important meetings out of breath and slightly clammy. Enter the e-bike. It may have a bad rep in the style stakes, lurking somewhere between Segways and those weird two-wheeled hoverboards, but sales of e-bikes reached $16bn (£12bn) globally in 2016, with forecasts of more than $24bn (£19bn) in 2025. With plenty of new operators in the space, including hip-hop mogul Mr Sean “P Diddy” Combs, it’s only a matter of time before they become socially acceptable. More seriously, however, there were 125 recorded cyclist deaths in the UK last year and, although e-bikes offer ease, they don’t provide better safety. Until roads are made more hospitable for cyclists, it looks like we’ll be locked in our cars for a little longer.

One thing city-dwellers are tired of being told is that we need to plant more trees. Most of us are cooped up inside exorbitantly priced flats that barely get any natural light, let alone have access to a garden. Once you start considering all the empty rooftops, window sills, pavements and parking lots in your neighbourhood, however, you’ll find a huge amount of wasted real estate ripe for a bit of guerilla gardening.

The urban allotment revolution of the past decade means you are likely to be well into retirement before you get an official place to grow your veg, but local councils in the UK are becoming increasingly amenable to green-fingered residents setting up mini gardens in disused spaces. Milan is leading the way here, with Mr Stefano Boeri’s Bosco Verticale (Vertical Forest), which was completed in 2014, alongside numerous green roof and vertical garden initiatives. A simple window box will do, but why not apply for permission to set up a few fruit crates of compost on your stoop and sow the seeds for a greener community? One major benefit of planting pollinating plants, such as foxgloves, honeysuckle or marjoram, is that they also boost the local bee population, which has been suffering from colony collapse in recent years. Membership of the British Beekeepers Association more than doubled to 23,000 between 2009 and 2015, with just one hive housing about 50,000 bees. Pollinators such as bees are essential to a healthy plant population, so what’s good for our furry friends is good for our greenery, too. Your neighbourhood could be about to get buzzier.

Last year, some scientists argued that we were entering a new geological era in the planet’s history. The whole of human civilisation has existed within the relatively stable Holocene era, but we could now be entering a far more turbulent Anthropocene (anthro- meaning human) era. The reason for this transition? Plastic-rock composites have been found on the beaches of Hawaii and great swirling land masses of plastic are forming as gyres in the world’s oceans. Some reports even suggest that the great North Pacific gyre is now bigger than the continental US. We are, quite literally, changing the geology of life on Earth.

Every year, it’s estimated that the US throws out enough clingfilm to wrap the state of Texas, while Americans use enough plastic drinking straws every day to circle the world two-and-a-half times. One of the highly publicised plastic perils of the modern age is the micro-beads that we use in face washes and shower scrubs, which can now be found at all levels of the marine food chain from molluscs to whales. This situation is clearly untenable and we need to make an effort to kick our addiction to polymers. We can do this on an individual level, of course, but relatively simple legislative action such the UK’s plastic bag tax can also have a massive impact. It’s thought that usage has dropped 80 per cent since the 5p tax was introduced in 2015.

It’s obscene that in an age where we still haven’t effectively tackled global poverty and starvation, developed nations throw away about 30 per cent of all food. Much of this waste comes from a western obsession with best-before and use-by dates, meaning that we’re all a little too bin-happy at home. Surprisingly, cheap durables such as rice, wheat and pasta are most often wasted, according to the United Nations, because people view them as disposable, cook too much and then throw away the leftovers. At the other end of the scale, expensive seafood is often chucked because of (quite valid) fears about food poisoning. The lesson here? Eat rich, perishable proteins on the day you buy them and look up a good egg fried rice recipe.

Another major factor in food wastage is purely cosmetic. We demand spherical tomatoes, straight cucumbers and gently curving bananas. The fact that nature doesn’t deliver to such exacting standards means that anything up to 40 per cent of fresh produce fails to find a market, according to the UN. This translates as 900 million tonnes of food rotting in storage or in the field every year because it’s not pretty enough. And there we were thinking the fashion industry was shallow…

There are numerous small, simple, everyday ways in which we can help build greener cities, but launching a personal crusade is only going to have so much impact. By far the most effective thing you can do is flex your democratic muscle and make your feelings known on a bigger stage. This might mean lobbying your local council or it could even mean standing for office yourself. Perhaps there’s a local green organisation you can join, or a park that you can volunteer at. Put pressure on corporations that are changing their practices too slowly. Vote with your wallet, but take to the streets if a bigger protest is needed.

Look to your own skill set, too. If you’re a writer, write about the problem. A lawyer? Look to legislation. Work in fashion? There are plenty of supply-chain issues to tackle here. All of us can enact change through our professional and personal lives, but perhaps the most important change of all is to help support the next generation in their quest to clean up our mess. Gen Z (those born in the 1990s) may have been dubbed Generation Snowflake because of their delicate demeanour, but they’re also born activists and are all too aware of the future perils they face. There’s a huge amount that divides us at the moment, but at a time when the leader of the free world has gone on record denying climate change, perhaps green issues can unite us, too.