Will London’s Ultra Low Emissions Zone improve the city’s health?

London. We think. Not sure, actually. Image: Getty.

A new Ultra Low Emission Zone (ULEZ) is being introduced in London, to reduce harmful emissions from traffic and improve air quality. Those who drive polluting vehicles into the city centre will face a daily charge – £12.50 for cars, motorcycles and vans, and £100 for lorries, buses and coaches – on top of the existing congestion charge. By October 2021, the scheme will expand to cover an area 18 times larger.

The rationale for the ULEZ is clear: large numbers of people are living in areas with pollution levels well above the legal limits set by the European Union (EU). These limits are based on detailed evidence about the impacts of air pollution on people’s health – which can cause everything from short term effects like worsening asthma symptoms, to a loss of healthy years of life in the longer term.

Other cities across the UK and beyond will be watching closely, as London’s ULEZ is effectively a test bed to gauge the effectiveness of such schemes at clearing up air pollution and improving the health of residents.

Major health problems

Over recent years, several London-based studies have shown that the city’s air pollution is associated with increased respiratory and cardiovascular hospital admissions, increases in daily deaths, stroke risk and low birth weights, as well as reduced lung volumes in children, dementia among the elderly, and poor mental health in children and adolescents.

Clearly, the polluted air that people breathe in London is having profound effects on their health, throughout their entire lives. So, while some people will lose out – for example, those who need to drive in central London for work – that should be weighed against the clear need for action to reduce pollution, on health grounds.

As well as the current health concerns, there are legal reasons why London authorities have introduced the new charge. Much of the area covered by the ULEZ often exceeds the annual EU limit for nitrogen dioxide (NO₂) – especially near roads, where diesel vehicles are a major source of the gas. The EU annual limit for NO₂ is 40μg/m³ (that’s micrograms per metre cubed).

A map of annual mean NO₂ pollution levels across London, based on data from 2013. Areas coloured from yellow through to red exceed annual targets. Image: London Air/KCL.

There are also other legal limits set by the EU for airborne particulate matter of various sizes. If you consider fine particles – often referred to as PM₂.₅ (generally less than 2.5 microns in diameter) – then the picture looks better. Most of London meets the EU’s annual limit for PM₂.₅, which is 25μg/m³.

But numerous studies have shown there are clear health impacts below this concentration, and the World Health Organisation (WHO) recommends that an annual target of 10μg/m³ would be best to protect people’s health. If this lower annual exposure limit was to be used, many areas across London would exceed it – just as they currently do with NO₂.

Medicine worth taking

The evidence shows that diesel exhaust emissions are the major driver of poor health outcomes due to air pollution. That doesn’t mean that other pollutant sources, such a biomass burning, agriculture, industry, or particles derived from brake and tyre wear, are not important – but it makes sense for cities to make reducing diesel emissions a priority. Will it work, though?

The ULEZ, like the Low Emission Zone before it, is designed to encourage the uptake of newer, low emission vehicles both by businesses and the general public with the aim of reducing air pollution in the target area. Current evidence does suggest that air pollution concentrations are falling in London as a result of several measures, such as the Low Emission Zone, but these improvements still need to be accelerated to deliver health benefits.


Since the ULEZ targets all vehicles, modelling commissioned by the Greater London Authority predicts that it will have significant impact on air quality, compared with earlier policies, which focused on restricting only certain types of vehicles. But this projection still needs to be validated.

If the ULEZ is the equivalent to the treatment to the air pollution problem, then like a clinical drug trial it requires independent evaluation, measuring both the changes in pollution concentration, and health improvements among Londoners.

Work is already ongoing to address these issues, such as the Children’s Health in London and Luton (CHILL) project, which is examining children’s respiratory health and lung growth across the introduction of the ULEZ. But further work evaluating this scheme is needed, to keep ensuring that policies are developed based on evidence – and prove to the public that this is a medicine worth taking.

The Conversation

Ian Mudway, Lecturer in Respiratory Toxicology, King's College London.

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

 
 
 
 

Here’s how we plant 2 billion more trees in the UK

A tree in Northallerton, North Yorkshire. Image: Getty.

The UK’s official climate advisor, the Committee on Climate Change (CCC), recently published a report outlining how to reduce the 12 per cent of greenhouse gas emissions that come from land use by two thirds by 2050. Alongside recommending cutting meat and dairy consumption by 20 per cent, the report calls for the annual creation of up to 50,000 hectares of broadleaf and conifer woodland for the next three decades. This would increase forest cover from 13 per cent to at least 17 per cent – a level not seen in Britain since before the Norman invasion.

Reforestation at that rate would mean creating roughly the area of the city of Leeds every year for the next three decades. At typical stocking densities of 1,500 stems per hectare, the ambition is to establish some 2.25 billion additional trees. Given that the UK, as with most of Europe, is in the grip of ash dieback, a disease likely to prove fatal for many millions of native ash trees, the scale of the challenge is massive.

On a crowded and intensively farmed island like Britain, unlocking a million and a half hectares of land will be no mean feat. But it’s not impossible – and is an unprecedented opportunity not only to tackle the climate crisis but also the biodiversity crisis that is every bit as detrimental to our wellbeing.

Trees and farms

One million and a half hectares is just 6 per cent of the mainland UK’s land area. To give some sense of perspective on this, 696,000 hectares of “temporary grassland” were registered in 2019. So if land supply is not the problem, what is? Often it’s cultural inertia. Farmers are firmly rooted to the land and perhaps understandably reluctant to stop producing food and instead become foresters. But the choice need not be so binary.

The intensification of agriculture has caused catastrophic declines in many species throughout the UK by reducing vast wooded areas and thousands of miles of hedgerows to small pockets of vegetation, isolating populations and making them more vulnerable to extinction.

Integrating trees with the farmed landscape delivers multiple benefits for farms and the environment. Reforestation doesn’t have to mean a return to the ecologically and culturally inappropriate single-species blocks of non-native conifers, which were planted en masse in the 1970s and 1980s. Incentivised under tax breaks to secure a domestic timber supply, many of the resulting plantations were located in places difficult or in some cases impossible to actually harvest.

Productive farmland needn’t be converted to woodland. Instead, that 4 per cent of land could be found by scattering trees more widely. After all, more trees on farmland is good for business. They prevent soil erosion and the run-off of pollutants, provide shade and shelter for livestock, a useful source of renewable fuel and year-round forage for pollinating insects.

The first tranche of tree planting could involve new hedgerows full of large trees, preferably with wide headlands of permanently untilled soils, providing further wildlife refuge.


Natural regeneration

Where appropriate, new woody habitats can be created simply by stopping how the land is currently used, such as by removing livestock. This process can be helped by scattering seeds in areas where seed sources are low. But patience is a virtue. If people can learn to tolerate less clipped and manicured landscapes, nature can run its own course.

A focus on deliberate tree planting also raises uncomfortable truths. Most trees are planted with an accompanying stake to keep them upright and a plastic shelter that protects the sapling from grazing damage. All too often, these shelters aren’t retrieved. Left to the elements, they break down into ever smaller pieces, and can be swept into rivers and eventually the ocean, where they threaten marine wildlife. Two billion tree shelters is a lot of plastic.

The main reason for using tree shelters at all is because the deer population in the UK is so high that in many places, it is all but impossible to establish new trees. This also has serious implications for existing woodland, which is prevented from naturally regenerating. In time, these trees will age and die, threatening the loss of the woodland itself. Climate change, pests and pathogens and the lack of a coordinated, centrally supported approach to deer management means the outlook for the UK’s existing treescape is uncertain at best.

An ecologically joined-up solution would be to reintroduce the natural predators of deer, such as lynx, wolves, and bears. Whether rewilding should get that far in the UK is still the subject of debate. Before that, perhaps the focus should be on providing the necessary habitat, rich in native trees.

A positive response would be to implement the balanced recommendations, made almost a decade ago in a government review, of creating more new habitat, improving what’s already there, and finding ways to link it together. Bigger, better, and more connected habitats.

But the UK is losing trees at increasing rates and not just through diseases. The recent removal of Victorian-era street trees in Sheffield and many other towns and cities is another issue to contend with. As the climate warms, increasing urban temperatures will mean cities need shade from street trees more than ever.

Trees aren’t the environmental panacea that the politicians might have people believe – even if they do make for great photo opportunities – but we do need more of them. Efforts to expand tree cover are underway across the world and the UK will benefit from contributing its share. Hitting the right balance – some commercial forestry, lots of new native woodland and millions of scattered trees – will be key to maximising the benefits they bring.

Nick Atkinson, Senior Lecturer in Ecology & Conservation, Nottingham Trent University.

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