Lessons from slums show why our cities need to go on a resource diet

The Mumbai slum Dharavi in 2007. Image: Getty.

Cities are the epicentres of human activity. They cover less than 2 per cent of the earth’s land surface but generate about 70 per cent of GDP and house more than half the human population. The importance of cities is only going to increase in coming decades as another 2.5bn people move to urban centres.

This intense production and consumption requires huge quantities of natural resources. Cities account for more than 60 per cent of global energy use, 70 per cent of greenhouse gas emissions and 70 per cent of global waste. Current practices are depleting the Earth’s finite resources, changing its climate and damaging its natural ecosystems. With our planetary life support system in the red, we need to put cities on a serious resource diet.

Resources efficiency in the New Urban Agenda

The New Urban Agenda adopted at the Habitat III conference outlines a vision for sustainable urban development. These global guidelines, along with the related UN Sustainable Development Goals, recognise the need to use resources more efficiently.

Habitat III included a number of sessions on resource efficiency and associated tools and initiatives. Organisations such as UNEP, UN-Habitat and the European Commission and its research centres typically led these events. The New Urban Agenda includes many references to efficiency and reduced consumption in cities.

We must now act urgently to translate words into actions. This will ease pressure on ecosystems and produce a range of co-benefits, including health, wellbeing and resilience.

How do we create more resource-efficient cities?

Cities use resources directly, such as burning fossil fuels for electricity and transport. However, indirect uses, such as water for growing food crops, are much wider-reaching.

It can be overwhelming to consider the resources used for all goods, processes and infrastructure in cities. Yet it is possible to measure this using a systems approach. Instead of considering components in isolation, the entire city is considered as an open system, connected to others.

This perspective ensures a much broader understanding of complex relationships between scales, resource flows, the built environment, socio-economic factors and ecological outcomes.

There are tools that embrace a systems perspective. For example, the urban metabolism approach considers cities as ecosystems, across which flows of resources (such as energy or water) are measured. Life cycle assessment measures resource use through the entire production, consumption and degradation process of a good or service.

These approaches have been successfully applied at various scales such as cities, neighbourhoods and buildings. This reveals that we are using more resources than shown by traditional assessment techniques (see this example on building energy efficiency regulations).

But measurement without action has no impact on the ground. How can these tools be used to transform our cities?

Recent research enables us to map the quantities of materials in buildings and predict when and where we can reuse or recycle these. Here a map of estimated steel quantities in each building of Melbourne, Australia. Source: authors' own; left: Google and TerraMetrics; right: Stephan, A. and Athanassiadis, A. (In Press) Quantifying and mapping embodied environmental requirements of urban building stocks, Building and Environment.

Many initiatives are targeting urban resource efficiency. The circular economy paradigm is a good example, where materials are reused, upcycled and recycled. It demonstrates that waste is a human concept and not an inherent property of cities. Waste does not exist in natural systems.

A range of projects by UNEP, the European Commission and other organisations support local resource efficiency initiatives and encourage local governments to implement related regulations. Blogging, data visualisation and disseminating research all help promote the adoption of resource efficiency concepts. In addition to the pioneering work of groups such as metabolism of cities, the uptake of open data is helping with this.

Learning from those who already live on less

Informal settlements provide interesting lessons in resource efficiency. Construction materials in these settlements are typically not very durable. However, because they are in short supply, they are constantly reused or repurposed, almost never discarded.

Other residents often reuse replaced materials, such as metal sheets, or store them for later use. This practice avoids additional resource use to produce new materials.

Although informal slum areas are often the focus of “upgrading” and improvement, lessons learnt in these settings can enhance material flow management and reduce waste elsewhere in cities.

Informal settlements like Karail next to Banani Lake in Dhaka, Bangladesh, can offer lessons in resource efficiency, waste reduction and material flow management to most cities. Image: Alexei Trundle.

Co-benefits of resource efficiency

More resource-efficient cities tend to result in better health outcomes. For instance, encouraging walking, cycling and public transport instead of car use can reduce fossil fuel consumption and greenhouse gas emissions, and improve population health through increased physical activity.

Food systems that promote consumption of fresh, local produce can benefit both the environment and nutrition. Energy-efficient housing reduces energy and water use and can improve occupants’ health at the same time.

Resource efficiency can also contribute to urban resilience. Nature-based solutions use relatively few non-renewable materials to increase resilience to environmental change and natural disasters. For example, a park can be designed to be flooded during storms or a tsunami, reduce the urban heat island effect, support urban ecosystems and provide areas for community activities, recreation and urban agriculture.

Efficiency can also ensure that redundancy – a core principle of resilience – is built into urban systems. This means resources can be repurposed in the event of an unanticipated shock or stress. For example, during the recent blackout in South Australia, a household with solar battery storage was able to maintain power for 12 hours “off grid”.


Working together for better solutions

Although these steps move cities in the right direction, more action from governments, the private sector and civil society is needed to transform our growing urban footprints.

Focusing solely on resource efficiency may neglect opportunities to generate co-benefits across sectors and will not provide robust solutions. We need to look at the entire city as a system and work together, across all disciplines, with effective and strong governance structures that support integrated policy definition and long-term implementation. If we don’t, we might simply shift a problem from one area to another, increase resource demand elsewhere, or create social divisions and tensions.The Conversation

Strong leadership, political stability, effective institutions and awareness-raising among citizens are vital factors for success. Urban resource efficiency is critical, but it should be considered along all other pressing issues highlighted in the New Urban Agenda.

This article was written by a team of researchers at the University of Melbourne. André Stephan is a postdoctoral research fellow; Alexei Trundle a PhD candidate in the Australian-German Climate & Energy College; Dave Kendal a researcher with the Royal Botanic Gardens Victoria (ARCUE); Hayley Henderson a PhD candidate in urban planning; Hesam Kamalipour a PhD candidate and research assistant in urban design, and Melanie Lowe a research fellow at the McCaughey VicHealth Community Wellbeing Unit of the Melbourne School of Population and Global Health.

This article was originally published on The Conversation. 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.