Awareness of the complex relationship between water, energy and food security has grown in recent years. Water is needed for almost all forms of energy production; energy is needed to transport and treat water; and producing food requires both energy and water. These are just a few of the linkages in the so-called energy-water-food nexus.
In the coming decades, population growth and social and economic development could cause a demand, supply and environmental crisis that will affect all three. By 2030, water supply could face a 40% shortfall, with the world's food needs growing by as much as 50%. By 2050, energy demand will be three times greater than it was a mere decade ago. It is therefore critical that we understand the connections between these three stresses, and examine what opportunities and risks they pose.
Urban development, population density and infrastructure quality have an obvious impact on the efficiency of energy and water use, and the availability of land for agriculture. Currently, cities are home to over 50% of the world's population and are responsible for up to 80% of CO2 emissions. With the proportion of people in cities expected to grow to 75% by 2050, it is clear that cities, and how they are developed, will have a huge influence on the environment and the demand for energy, water and food.
Cities must be compact and connected, with energy-efficient public transport, environmentally friendly buildings and secure access to water and food. They must also integrate transportation, energy, water and waste systems that are much more effective than those of today.
For energy to play its part, it must first tackle the problem of energy loss. According to research conducted by the International Energy Agency on energy usage in cities, over half of primary energy ends up as low-grade waste heat that is emitted by transport and power generating facilities.
To counter this, waste released from transport could be reduced by means of promoting fuel economy standards, lighter vehicles and electric vehicles, as well as implementing a smarter approach to freight management.
From a power generation perspective, Combined Heat and Power (CHP) solutions - such as well-designed district heating schemes, and the use of more energy-efficient gas-fired power stations - can be employed to significantly reduce waste heat.
However, central to achieving a harmonious water-energy-food nexus is investment and knowledge-intensive innovation. Both of these do not necessarily require new technologies or inventions. Instead, they depend on innovation in design, planning, land use management, increased efficiency, demand and supply integration, and consumer choice.
They also require policy frameworks that both encourage innovative private-sector investment, and provide a degree of regulatory stability in the face of anticipated economic and political volatility.
Between now and 2050, it is estimated that the development of city infrastructure will account for more than US$300 trillion in building and running costs. Close collaboration is required between the multiple stakeholders, including urban planners, local governments, and companies involved in transport, infrastructure, construction, IT and energy. Without it, rapid urbanisation risks leading to chaotic urban sprawl, pollution, the disappearance of fertile agricultural land, and more pressure placed on valuable water and food resources.
To achieve a sustainable urban future, tomorrow's cities will have to rely on close collaboration between private and public sector bodies. We can be more innovative in tackling these tough challenges together, than we can be separately.