To achieve an objective, in a world of limited resources, it is important to be efficient. If, in addition, this objective requires an urgent response, getting the selection of the actions to be taken right becomes crucial.

In the fight against climate change - a global, necessary and urgent objective - we have privileged information that puts us in a good position to act. We know for certain who is responsible for 60% of greenhouse gas (GHG) emissions and for consuming 78% of the world's energy[1], and we know where to find them. We are talking about cities.

Cities are concentrated in only 2% of the earth's surface and we have their exact location. However, this is not a simple task because it is well known. Urban environments are complex and present a multitude of interactions that need to be considered in order to aspire to meet the objectives set out in the United Nations 2030 Agenda (the Sustainable Development Goals).

As we gathered in the study "Climate Change and Cities: Business Action", published in November 2017, we are facing a great challenge that poses a myriad of opportunities, which have even been economically valued at $3.7 trillion in savings and new opportunities[2]. To begin with, according to experts, cities are and will be in the not so distant future the environments that will house, not only most of the world's population, but also an important part of economic activity.

By 2050, it is estimated that 70% of the global population will live in cities[3], which roughly implies - taking into account population growth - that cities alone will concentrate the equivalent of today's total population. Cities must therefore become truly resilient environments, capable of adapting quickly to economic, social and environmental changes, while maintaining a decent quality of life for their inhabitants. A sustainable urban environment is the only viable alternative to ensure a better life for citizens, efficient use of resources and economic prosperity.

In the Paris Agreement, cities - and therefore their governments, the organizations and companies that operate in them, and their citizens - are called upon to take ambitious action in the fight against climate change. It is important to understand the dual approach of cities to climate change. On the one hand, as a generator of impacts: mainly through consumption and production patterns and their consequences. On the other, as a vulnerable recipient of its effects: people's quality of life, health and assets, especially for the most vulnerable population, will be affected by the rise in sea level, rainfall and flooding or the increase in the frequency of weather events and extreme temperatures.

It is essential that cities increase their resilience to climate change and favor a transition towards low-carbon city models. Climate action is necessary and urgent in terms of mitigation and adaptation of cities.

As cities become more relevant actors in climate action, there is also a greater need for private sector funding and involvement. Thus, there is an urgent need to expand engagement models that allow cities and businesses to collaborate from the earliest planning stages and leverage the full innovative capacity and resources of the private sector.

Aware of this situation of change in the way we work and face the great global challenges, the 50 large companies that make up the Climate Change Cluster promoted by Forética in Spain, have wanted to delve deeper into this issue during 2017 and have identified five levers through which progress can be made towards the consolidation of sustainable cities through public-private collaboration: sustainable mobility, energy efficiency and the promotion of renewable energies, the development of smart infrastructures and connections, the promotion of sustainable and healthy lifestyles, and the commitment to financing and innovation in the service of climate action.

According to the study, the keys to successful collaboration between companies and cities include: incorporating the relationship from the earliest stages of strategic planning, establishing a working relationship based on transparency and trust, and improving the level of understanding of the needs of cities, as well as the responsiveness of the private sector in terms of available technologies, commercial models or business strategies based on sustainability. This working approach will enable companies to capitalize earlier on the benefits and opportunities derived from the solutions developed, to maintain their activity in a more efficient and sustainable way and to favor the quality of life of city dwellers and consumers, contributing to solving today's sustainability challenges and creating long-term economic viability. According to the World Business Council for Sustainable Development (WBCSD), for forward-looking companies, the New Urban Agenda is the new business agenda.

We know that cities are key players in the fight against climate change. Understanding and collaboration between governments, the business sector and citizens are the keys to the development and implementation of the most efficient actions to achieve this. Let's act, it is the only option. "The battle for sustainable development will be won or lost in cities" Joan Clos, Executive Director of UN Habitat.

[1] World Business Council for Sustainable Development http://www.wbcsd.org/

[2] Business and Sustainable Development Commission http://businesscommission.org/

[3] UN Habitat https://unhabitat.org/urban-themes/climate-change/

Published on January 19, 2018 in El Economista's Good Governance and CSR magazine (page 14).