Sustainability in the 21st century

1. Sustainability and sustainable development

Sustainability was first defined in ecology as the property of biological systems to remain diverse and productive indefinitely. Diversity is an essential requirement for a system to be flexible and able to adapt, which in turn is a necessary condition to survive to shocks. An example are healthy forests that proved to be able to survive for very long time in good conditions notwithstanding the impact of several environmental changes. Another example is the ocean. The concept of sustainability can be extended to any environmental, political and economical system. Today, there is increasing evidence that environmental systems are strictly connected with human systems like political and economical ones, and therefore there is increasing awareness that sustainability of the whole earth system is linked with a two way interaction with human actions. For this reason, sustainability recently became an extremely debated issue.

In 2005, the World Summit on Social Developmen identified sustainable development goals. This view has been expressed by a graphical representation by using three overlapping ellipses indicating three pillars of sustainability:

  • economic development;
  • social development;
  • and environmental protection.

The pillars have been recognized as not mutually exclusive but rather mutually reinforcing. In fact, the three pillars are interdependent, and in the long run none can exist without the others (see Figure 1).

Figure 1. The three pillars of sustainability. Note that economy and society are constrained by environmental limits. By KTucker - Own work, CC BY-SA 3.0,

The intersection among the three pillars is shown in Figure 2. The intersection between social and environmental pillars identifies the bearable strategies; the intersection between social and economics pillars identifies the equitable strategies, while the intersection between environment and economic pillars corresponds to viable strategies. Finally, the intersection between bearable, equitable and viable strategies identifies sustainable ways forward.

Figure 2. The three pillars of sustainability and their intersection. By original: Johann Dréo (talk · contribs)translation: Pro bug catcher (talk · contribs) - Own workInspired from Developpement durable.jpgTranslated from Developpement durable.svg, CC BY-SA 3.0,

Integral elements of sustainability are research, innovation, education, technological transfer and policy making. An example of policy towards sustainability is the European environmental research and innovation policy, which aims at defining and implementing a transformative agenda to greening the economy and the society as a whole so to make them sustainable.

Sustainability is closely connected to resilience of the related systems. Resilience was first defined in ecology as the capacity of an ecosystem to absorb disturbance and still retain its basic structure and viability. In the context of sustainability of environment, economic and society, resilience implies the need to manage interactions between human-constructed systems and natural ecosystems in a sustainable way. Resilience-thinking addresses how much systems can withstand the human impact while still delivering, to the current and future generations, their needed services.

Sustainability is strictly connected to the concept of sustainable development. It is defined as a set of strategies to meet human development goals while at the same time sustaining the ability of natural systems to provide the natural resources and ecosystem services upon which the economy and society depend. The concept of sustainable development is subject to criticism, as on the one hand the whole Earth system, even in natural conditions, is not sustainable, as the history of other planets like Mars clearly shows. There is increasing evidence that Mars was once hosting water and maybe some forms of life, but the evolution of the planet caused the loss of water. On the other hand, human actions may help to achieve sustainability, through the management of the natural evolution of the Earth system. The human management of water resources is a clear example where the human intervention may support the conservation of ecosystem and may shape the evolution of the landscape in a more sustainable manner. The concept of sustainability should be linked to the need of making the best possible use of Earth resources, including water, energy and food, with the awareness that future evolution and research innovation may be unpredictable, and the awareness that the processes governing the Earth system are affected by intrinsic uncertainty (think, for instance, at the impact that a planetary collision may have).

The United Nations have recently developed the sustainable development goals to end poverty, protect the planet and ensure prosperity for all as part of a new sustainable development agenda. Each goal has specific targets to be achieved over the next 15 years. For the goals to be reached, everyone needs to do their part: governments, the private sector, civil society and people like us.

2. Sustainability concepts for water resources management

Sustainability of water resources is a topical issue today in view of the increasing occurrence of water scarcity, which is defined as the lack of sufficient available fresh water resources to meet water demand. Water scarcity was listed in 2015 by the World Economic Forum as the largest global risk in terms of potential impact in the near future.

In the context of water resources management, sustainability can be defined as the property of water resources systems to remain functional in the long term. Note that the definition refers to the global plurality of water resources system, and therefore not only at their local function. In fact, water resources are sometimes mismanaged because water is considered a local good and water issues are often treated as local problems. The reason is that water management is often planned at the local level, because water in itself is complicated to move far from its current location. Therefore, one essential premise for sustainable water resources management is the adoption of a global perspective, which should necessarily lead to a global water policy. Science is moving forward along this direction by promoting global modeling and global assessment of water resources.

Of course local management remains the fundamental piece to build the whole puzzle, but each of these pieces need to be placed in the right position and with a design that needs to compose a coherently shaped whole picture. To reach the target, it is necessary that local design takes into account:

  • Water resources assessment;
  • Lifetime of the water resources system;
  • Societal development during the lifetime of the system;
  • Changes in water resources status during the lifetime of the system, which may be due to local anthropogenic impact and climate change;
  • Resilience of the system to societal development and changes in water resources;
  • Afterlife of the system, including opportunities for recovery and renovation;
  • Interaction with governance at local, regional and global scale.

The first two items are traditionally explored by hydrologists and water resources engineers, with consolidated methods that are still valid in the presence of change and increasing societal development. However, we should note that the interdependencies and feedbacks between the different hydrological cycle components and society are often not fully appreciated. It is increasingly clear that hydrology and humans are connected through a two-ways interaction whose feedbacks and the related uncertainties need to be taken into account. However, we often do not have enough data for design and therefore research questions arise about the estimation of design variables in absence of sufficient data resources. Also, water quality monitoring programmes are inadequate or lacking in several nations; despite two decades of increased international scientific attention and concern, attempts to collect, compile and gain knowledge from consumption, pollution and abstraction data and information at a global scale are still not satisfactory, although we do see relevant progresses, mainly due to new monitoring technologies.

The last item is the key for making an efficient and optimal design successful. Connection with governance and the public is essential for a proper use of water resources, which in turn requires "social learning". The latter is an essential element of policy development and implementation, that is supposed to enable us to to develop a timely and adequate response to the changing dynamics of social–hydrological systems in concrete contexts of action. When turning to the practical implementation of measures, we often experience the challenge that the governance and social systems do not respond as expected, for several reasons ranging from political conflict, insufficient economic resources, inefficiency of administration and so forth. The problem has been recently exacerbated after the introduction of participatory approaches in water resources management, and the widespread dissemination of information and knowledge. In fact, wee still lack objective methods for developing a synthesis of different and diverging opinions. Scenario analysis, that is, the process of analyzing possible future events by considering alternative possible outcomes, helps in assessing the likely outcome from different policy alternatives, but still its use is often not convincing in view of its uncertainty and the frequently skeptical attitude of stakeholders.

Social learning entails developing relational capacities to learn how to collaborate and understand others’ roles and capacity, by taking into account institutional arrangements and the social context. Therefore, the problem lies in developing new identities, as well as institutions and individual capacities, that are more socially and ecologically robust with the common goal of sustainability. The interdisciplinary collaboration between geoscience and social science is essential in this respect, where each discipline should assume the role that is pertinent to its background and knowledge. The connection between engineering and society necessarily needs to be supported by social and political sciences.

Societal development and change are driving forces that, when combined with the pressures from economic growth and major population change, make the sustainable development of water resources a challenge. The combination of these drivers usually results in increased water use, competition and pollution in addition to inefficient water supply. These results can be traced back to local and short-term decisions in water resources management that lack the global and long-term vision needed to implement sustainable development.

The role of research and education is much relevant in this context. Change in hydrology and society is the subject of the international research decade 2013-2022 "Panta Rhei", promoted by the International Association of Hydrological Sciences, which is currently organizing a global effort to stimulate research about sustainable water resources management.

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Last updated on February 27, 2018