Over the past decades, the frequency and severity of extreme weather events are rapidly increasing due to climate changes. These events, represented by flooding, drought, heavy rain, tropical cyclone, heat waves, or cold waves, have often caused various damages not only in the short term but have also had various long-term effects, such as sea level rise and spread of disease. The negative impact of these events has been highlighted by the Intergovernmental Panel on Climate Change (IPCC, 2014). Nevertheless, across the world, severe weather events such as typhoons, heavy rains, and changing patterns of meteorological disasters have already caused the loss of many lives and built assets. These damages are likely to accelerate in the future.

It is well known that natural disaster-triggered losses are very closely tied to many economic losses worldwide. For example, Western European countries such as France, Germany, and Switzerland were hit by three consecutive tropical cyclones (e.g. Anatol, Lothar, and Martin) in 1999, resulting in a loss of EUR 13 billion. Typhoon Haiyan, which hit the Philippines and China in 2013, as a Category 5 Super Typhoon, was the most extreme tropical cyclone recorded on land. The typhoon's life-threatening wind and rain were enough to smash properties. South Asian countries adjacent to the typhoon track suffered about USD 300 billion in damage. Hurricane Katrina which hit south-eastern areas in the United States in 2005 caused the most severe damage in the national historic record as a Category 5 tropical cyclone. In detail, it caused USD 180 billion in direct and indirect damages to US Gulf Coast cities due to substantial rain and robust winds. Later, in 2017, three different strong hurricanes named Harvey, Maria, and Irma together caused a total amount of about USD 293 billion in damage, based on the individual damage amounts of USD 125 billion from Harvey, USD 90 billion from Maria, and USD 77.6 billion from Irma.

In this sense, the quality of living in the built environment has been threatened by natural disasters across the globe. To reduce these threats, many non-governmental organizations and countries have investigated prevention or post-disaster recovery strategies, considering aspects of time, budget, and human capacity to mitigate natural disaster risks. Mitigation of risks can reduce the loss by decreasing vulnerability or by decreasing the frequency and severity of causal factors. For risk mitigation, the execution and allocation of financial resources should be carried out promptly and extensively, with the limited resources available. Hence, it is important to estimate strategically the cost impact of natural disaster risks and the effect of risk reduction at the same time, specifically aiming at achieving the ultimate reduction and mitigation of risks through the efficient use of limited resources.

Disasters Risk Reduction and Nature-Based Solutions

The Sendai Framework for Disaster Risk Reduction 2015–2030 outlines four basic action priorities that must be considered: (1) understanding disaster risk; (2) strengthening disaster risk governance to DRR; (3) enhancing disaster preparedness for effective response, recovery, rehabilitation, and reconstruction; (4) investing in structural and non-structural measures for resilience.

Normally, a disruptive event opens the way for a shift of state that can display early-warning signals of a collapse. In this case, the loss of social and ecological ability to recover from a disturbance such as an environmental or technological disaster endangers the services derived from nature. On the opposite, resilience expresses the degree to which an ecological system can be recovered and continue functioning. Adaptation to climate change is seen as a key element toward resilience, developed through an operational framework that allows local planners to define approaches and practical strategies for action. Therefore, it is fundamental to understand the dynamic of the whole system and to develop frameworks that recognize the multiple values of NBS and their co-benefits for society since it represents a valuable tool for the decision-making process.

In recent years, EbA has been recognized as an effort to integrate biodiversity and ecosystem services in an adaptation strategy to reduce vulnerability to climate change. This approach emphasizes the importance of ecosystems in effective climate change adaptation (CCA) and DRR. The DRR has been the subject of important discussions in the ecosystem management field that has lately emerged as an alternative to mitigate the impacts of extreme events and improvement of environmental resilience. This urgency has strong policy support, including the Millennium Ecosystem Assessment within the framework of the Sustainable Development Goals, and the Strategic Plan for Biodiversity 2011–2020 under the Convention on Biological Diversity. For this reason, ecosystem-based disaster risk reduction (Eco-DRR) has also gained increasing attention. Successful adaptation requires an understanding of interactions within socio-ecological systems, consequently, it can be guided to Eco-DRR. In practice, EbA and Eco-DRR operate under different political arenas and are often driven by distinct institutions reflecting basic differences that can be observed such as (1) CCA covers long-term mean changes in climate and their impacts on social ecosystems; (2) DRR has an emphasis on a warning system, monitoring, response, recovery, and reconstruction after a disaster; (3) both present divergences in terms of operational instruments and implementation due they have slightly different focuses. Nonetheless, they have much more in common than differences because the ecosystem-based approaches can connect the DRR and CCA fields. NPS is defined by International Union for Conservation of Nature (IUCN) as the actions to protect, manage and restore natural or modified ecosystems to address societal challenges such as CCA. The concept emerged from ecological science and the nature conservation field. It was introduced by international organizations (e.g. IUCN and European Union) which were looking for solutions to work with the ecosystem rather than conventional engineering (i.e. gray infrastructure) to adapt to climate change.

The NBS covers a wide range of practices that are based on the management of ecological processes such as conservation and restoration of the ecosystems, maintaining biodiversity and the natural habitats, making part of integrated actions to support resilience and provide adaptation benefits. The concept based on the statement that nature provides ecological services is extremely simplistic. The NBS principles aim to be inspired by nature and how it works, which means creating conditions for ecological solutions linked with human activities. In other words, the NBS perspective is based on the idea of being intimately connected with nature. For example, we can verify a combination of NbS such as agroforestry systems with restoring wetlands for local food supply or flood risk mitigation with the restoration of mangroves for protection of estuary and nursery management. In the same way, a recent study about the hydrological effect of vegetation on rainfall-induced landslides quantified the main hydrological mechanism contributing to slope stability. Nonetheless, it is necessary to highlight that there is a significant difference between NbS and EbA. The concept of EbA is related to the capacity of nature to protect human communities against the adverse impacts of climate change through ecosystem services delivery. EPA seeks to balance ecological conservation and management of the human system to enhance the range of opportunities and benefits provided by nature as well as to increase the number of stakeholders with distinct interests.

Individuals and societies are no longer connected in such a way as to ensure a sustainable future. Naturally, this leads to reflecting on some important aspects: (1) the need to work with nature's likeness by requiring a similar process of natural evolution, and (2) the management of the ecosystem's ability to focus on new governance forms with distinct accountability processes. Practical progress is required to improve resilience by delivering ecosystem services to meet societal challenges such as the population's protection needs through the incentive of ecological innovations. The purpose of the NBS is to reduce a range of interlinked pressures caused by degradation such as water pollution, soil sealing (compactness) through expansion of built-up areas, deforestation from illegal logging, agricultural production with irreversible biodiversity loss to comprise a wider definition of how to conserve the biological attributes and use the ecosystem services aligned with innovation perspectives without to aggravate the local vulnerability.

Despite the variety of many scientific theories, there are fundamental principles that should be considered when working with NbS. One of the most essential would be the complexity of socio-ecological systems and the fact that they are dynamic. Another is that incorporating ecosystems in DRR can save lives, aid recovery, and help to build more resilient environments. For instance, if the adaptive decisions neglect that urban growth can influence the environmental exposure level, they also ignore the retroactive effect in hazard assessment and on the vulnerability of people. Normally, they fail to sufficiently anticipate consequences which results in incorrect solutions.

About the Author: Syed Asad Raza is an environmentalist with a keen interests in environmental conservation and protection.