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Should We Curb City Growth to Feed the Planet?

Pressures on land

Unless the burgeoning expansion of cities into agricultural land is curtailed the world could face huge problems feeding an expanding population by 2050, according to the United Nations Environment Program.

More and more land is being converted to crop land at the expense of Savannah, grassland and forests, reducing the world's biodiversity. Agriculture now consumes over 30% of total global land area, split into one third crops for human and animal consumption and one third grazing land.

This amount has expanded by 11% between 1961 and 2007.

(Right: the pressures on land use.)

Several ways are suggested of curbing the voracious appetite of humans for land for food:

  • reducing food waste: over half of food grown is wasted along the production line;
  • building more dense cities so that a more efficient use is made of available land;
  • increasing vegetarianism; in the unlikely event of the world totally converting to a meat free diet the amount of land area required would shrink by over two thirds.

UNEP has based its call on a report that was launched at Davos entitled Assessing Global Land Use: Balancing Consumption with Sustainable Supply. It was produced by the International Resource Panel: a consortium of 27 internationally renowned resource scientists, 33 national governments and other groups, coordinated by Prof. Dr. Stefan Bringezu, Head of Research Group 3 at the Wuppertal Institute.

"The findings of the International Resource Panel show that the world has witnessed an unprecedented sharp decline in terrestrial ecosystem services and functions during the past decades," said UN Under-Secretary-General and UNEP Executive Director Achim Steiner, launching the report. "Forests and wetlands have been converted to agricultural land to feed growing populations but at a cost that is not sustainable."

"We need to become more efficient in the ways we produce, supply and consume our land-based products. We must be able to define and adhere to the boundaries within which the world can safely operate to save millions of hectares by 2050," he urged.

The report says that by 2050 upto 70% of the world's population could live in cities. The UN expects that "urban areas will absorb all the population growth over the next four decades".

Population growth and urban sprawl

The report discusses patterns of urban expansion in different areas of the world. For example, the highest relative increase between 1950 and 2010 was in Africa where there was a 12 times rise in urban population.

World population growth graph

The proportion of people living in these areas is higher in developed countries than in less developed ones and is projected to increase as well towards 2050, although at a more moderate rate than in less developed countries. This is because population densities of cities in developing countries are generally three times higher than in industrial countries.

 population growth and land use graph

However, the densities of cities everywhere have been decreasing, associated with urban sprawl.

Urban sprawl is a problem because habitats and biodiversity are lost and there is a greater demand for natural resources. The size and spatial configuration of urban areas directly relates to increased energy and material flows such as carbon emissions and infrastructure demands.

 population, land use and agricultural food supply trends graph

The European Environment Agency describes sprawl as the physical pattern of low-density expansion of large urban areas. It is the leading edge of urban growth and implies little planning control of land subdivision.

With sprawl, development is patchy, scattered and strung out. It leapfrogs over areas leaving enclaves of agricultural land. This leads to an inefficient use of land space: pockets of disused wasteland.

The space around urban areas which merges into the rural landscape is called 'peri-urban'. These areas are growing rapidly across Europe with about 48,000 kmĀ² of built development in peri-urban areas, almost equal to the urban areas.

Built development in peri-urban areas is growing at a rate four times faster than in urban areas (0.5-0.6% per year) in Europe. It is strongly linked to the high prices of already urbanised land versus the low prices of rural land, associated with relatively low transport costs. Sprawl therefore necessitates the development of transport networks, which themselves consume resources.

Somehow this growth must be contained

The report sets a limit on the amount of land that could be used for supporting each individual on the planet, called the "safe operating space" (SOS). Already people in developed countries are operating beyond this safe space, beyond which, if everybody on the planet did so, would push the planet beyond tipping points into environmental catastrophe.

For example in the European Union each person required 0.31 ha in 2007, which is one third more than that available for everyone on the planet, and one quarter more than is available within the continent's land area.

In other words current consumption levels are unsustainable, let alone those that are projected to occur in the future.

Currently biotech companies like Monsanto claim that their genetically modified seeds and Roundup herbicide are a solution to the need to feed growing populations.

But the report says that, by contrast: "the reduction of food loss and waste, the control of biomaterials consumption and improved land management and restoration of degraded land, may allow us to save 161 to 319 million hectares of land by 2050". Improving diet and reducing food waste alone could save between 96 and 135 million hectares.

The report also advocates improved resource management in cities and urban gardening.

The framework for resource management should be set, UNEP urges, at country level, improving land use planning to help prevent the loss of high-value nature areas due to expanding cities and expanding agriculture and livestock production. The protection of fertile soils should be prioritised.

Small farmers on marginal land are often the victims of land dispositions to make way for cities and massive agribusiness operations, and the report adds that their rights should be protected.

Ultimately, the responsibility lies with national and local governments to manage and plan land use in a much more efficient manner.