The Urban Planet

Productive land is lost to urbanisation

The Earth viewed from space – with 70 % of its surface covered with water – is called the Blue Planet. The remaining 30 % of terrestrial land surface is home to a human population of 7.6 billion and, in the age of the Anthropocene, it may be more appropriate to refer to it as the Urban Planet: More than half of the world’s population now reside in urban areas, despite these covering only around 3 % of the land surface (excluding Antarctica).
In 1900, only 10 % of the global population were urban dwellers. By 2014, this number rose to 54 % of the world’s population. This is a harbinger of a trend that is expected to continue. By 2050, the world’s population will be about one-third rural and two-thirds urban, roughly the reverse of the rural-urban mix of the mid-twentieth century.
It is generally accepted that the longterm consequences of urbanisation are complex and uncertain. On the positive side, urbanisation can lead to increased energy efficiencies, higher productivity and enormous economic benefits. The latter is especially true in emerging markets, which have
enjoyed rising incomes. This has shifted the global economic balance toward the east and south. On the negative side, there is no doubt that urban sprawl displaces species, alters water cycles, consumes irreplaceable wetlands and farmlands and is reshaping the global landscape. The land area needed to provide food, energy and materials to a city is often 200 times greater than the area of the city itself. As hubs of production, consumption and congestion, cities account for 70 % of the
world’s carbon emissions, which contribute to global warming. Cities are also a major source of aerosols (the “haze plumes”), which alter regional precipitation patterns. In addition, the
growth of cities alters land cover and land surface temperatures (one case study in South East China found that mean surface temperatures increased 0.05 ℃ per decade). Cities alter the environment via the widespread use of paved roads and roofs, which prevents water from infiltrating into the soil and thus promotes flooding and polluted runoff that damage aquatic
ecosystems. Cities are major sources of crime, noise, water and air pollution, “heat island” effects, artificial light and disease. These combined problems tend to be exacerbated in developing countries where currently about 0.9 billion city dwellers live in urban slums under dire social disparities. It is perhaps ominous that the overwhelming majority of new urban dwellers by 2050 will be in developing countries.

China's Urbanisation
China's urbanisation rate has been described by the World Bank as “unprecedented in scale. Over the past several decades, rapid urbanisation has profoundly changed the entire country’s social, economic and environmental core. The National Development and Reform Commission of China reported that the percentage of its population living in urban areas surpassed 56 % in 2016 and the government is targeting a value of 60 % by 2020. By 2050, it is projected that nearly 80 % of all Chinese residents will reside in cities (see Figure). Although urbanisation has been extremely beneficial for social and economic development, the long-term consequences for the environment are serious and challenging. Problems include land degradation, loss of arable land, depletion of natural resources, the pollution of soil, air and water, fragmentation of natural landscapes and decline in basic ecosystem services (e.g. water resources, crop pollination, carbon sequestration, food production). Perhaps one of the most pressing issues is the conversion of agricultural areas, such as rich farmland in the eastern coastal provinces, into urban centres. Arable land lost to development and contamination is frequently replaced by marginal and lower-quality alternatives. The National Land Resource Survey of China reported that the amount of available land in China has peaked yet rural land conversion rates continue unabated and have actually accelerated (based on 2008–2012 data). About 3 million hectares of high-quality arable land (plus an additional 1 million hectares of paddies) have been lost to urban use in the past 10 years. Hence, pressure on China’s farmland resources will inevitably continue, threatening its food security. A significant driver of the loss of arable land is the central government’s transfer of fiscal responsibilities of land management to local governments. This has created a “perverse incentive to exacerbate urban sprawl” since many local governments greatly benefit financially by shifting farmland to nonagricultural use and selling building rights (in some instances accounting for 40 % or more of a city's entire budget). Although the issues are complex and multidimensional, novel ways must be found to protect and better manage existing farmland and to reduce the loss of arable land. The remaining high-quality arable land is being overused, which leads to reduced fertility, soil erosion, acidification and heavy metal contamination. Increasing efforts are being made to reclaim and restore degraded lands. Overall, agricultural production has only slightly decreased in recent years but the continued loss of arable land, coupled with other forms of land degradation, will compromise the future of China’s food production systems. Simulation results suggest that for each 1 % increase in China’s urbanisation rate, there is a decline in 0.065 % of cultivated area and a 0.067 % decline in its agricultural production potential.

A comparison of past and projected urbanisation (% urban population) for China and the world. Some major sociopolitical events in the recent Chinese history are noted as key drivers of urbanisation (for an indepth analysis of these events). The black dot indicates the turning point when urban population became larger than rural.
Source: Redrawn from Wu et al.

World Urbanisation Prospects
Source:Population Facts, No 2014/3 August 2014. Department of Economic and Social Affairs, Population Division. © 2014 United Nations. Reused with the permission of the United Nations.

Among 233 countries or areas:

  • Just 15 % had levels of urbanisation greater than 60 %, i.e. more then 60 % of the population lived in urban areas
  • Only 6 % had more than 80 % of the population living in urban areas

World Urbanisation Prospects
Source:Population Facts, No 2014/3 August 2014. Department of Economic and Social Affairs, Population Division. © 2014 United Nations. Reused with the permission of the United Nations.

  • Estimates indicate that, in 2014, around half of all countries or areas had more than 60 % of their population living in urban areas and in 25 % of countries or areas the urban population exceeded 80 % of the total country population
  • Northern America and Latin America and the Caribbean are the most urbanised regions, with 80 % or more of their populations residing in urban settlements
  • Europe, with 73 % of its population living in urban areas in 2014, is expected to be more than 80 % urban by 2050

World Urbanisation Prospects
Source:Population Facts, No 2014/3 August 2014. Department of Economic and Social Affairs, Population Division. © 2014 United Nations. Reused with the permission of the United Nations.

  • Projections indicate that by 2050 in nearly 70 % of all countries or areas in the world the urban population will be more than 60 % and 38 % of all countries or areas will have more than 80 % of their population living in urban areas
  • Of the 2.5 billion new urban dwellers anticipated by 2050, 90 % will live in Africa and Asia. Nevertheless, they are expected to remain the two least urbanized regions of the world
  • India, China and Nigeria – together are expected to account for more than one-third of global urban population growth