Population growth and rapid urbanization are combining to create huge challenges for cities all over the world. Meeting demand for urban services in these cities will need massive capital investment over the years. The concentrations of people and their activities create intensified pressure on the environment. Cities consume around 75 % of the natural resources in order to sustain the various functions performed within them. Without the proper design and planning, this massive urban growth will inevitably exacerbate existing problems of congestion, pollution, environmental degradation, and resource scarcity, as well as social inequalities in resources access.
However, this very concentration and dynamics offer opportunities, through design and actions at an urban scale, to enhance resources efficiency, and in doing so, raise equitable access and minimize the various environmental impacts, including the effects of climate change.

Figure (1) Simplified model of Urban Metabolism - IMaREC

IMaREC focuses on natural resources efficiency in the built environment and aims at directing education and research towards achieving progress to the Sustainable Development Goals (SDGs):

• Goal 11 “Make cities and human settlements inclusive, safe and sustainable”, along with other SDGs such as
• Goal 6 “Ensure availability and sustainable use of water and sanitation for all”,
• Goal 7 “Ensure sustainable energy for all”, and
• Goal 9 “Promote sustainable infrastructure and industrialization and foster innovation”.

This concept comes also in line with the UNEP Initiative launched after the Rio+20 summit in Brazil 2012: "The Global Initiative for Resource Efficient Cities”.