Ecological resilience: how ecosystems adapt to change

The only thing that is permanent is change: everything is in a state of constant change – human societies and natural habitats – even if we’re not aware of it at first glance. Moreover, change itself changes, too: sometimes it’s slow and gradual, while at other times it’s sudden and disruptive. This is where the concept of ecological resilience comes in.

Ecological resilience: what it is

There are no universally agreed definitions of ecological resilience, but all of them – differences in wording apart – agree on one basic concept: the ability of a natural system to absorb the effects of change, reorganize itself and adapt to the new context while essentially maintaining its previous structure and functions.

In short, it is the ability to respond to change without altering its basic structure, or with only minor modifications.

The criteria we use to measure resilience also differ: one is the amount of external disturbance the system is able to handle; another is the time needed for the system to return to its previous equilibrium.

The origins and history of the concept

The term "resilience" was already in use in the 19th century in the field of materials science; in the second half of the 20th century, the concept was gradually extended to other fields – including, in particular, psychology. The first to talk about ecological resilience was Canadian ecologist Crawford Stanley Holling in his article "Resilience and Stability of Ecological Systems," which appeared in the Annual Review of Ecology and Systematics in 1973.

Today, ecological resilience is a widely studied field of research, partly because of its topicality and the extent of environmental problems, which, until a few decades ago, were only vaguely understood.

Specialized bodies and institutes have sprung up to address this issue, such as the Resilience Alliance, founded in 1999, and the Stockholm Resilience Institute, in 2007. There are also journals devoted to this line of study, such as Ecology and Society.

We often speak more generally in this context of socio-ecological resilience. This emphasizes human responsibility for the profound transformation taking place in the environment, but which in turn can have a negative impact on people and communities.

Even when the simpler term "ecological resilience" is used for the sake of brevity, the social and generally human aspects are still implied.

Resilience and resistance

It’s important to distinguish resilience from another concept with which it sometimes gets confused: resistance.
The two concepts are more intuitively understood by associating resistance with rigidity and resilience with flexibility.

Etymologically, the word "resilient" derives from the Latin word resilire, meaning "to bounce back."

In psychology, a resistant person is one who, despite adversity, holds on to his or her ideas, behaviors and habits.
The resilient person, on the other hand, is one who knows how to reflect on himself or herself and adjust.
Resistance is the tendency not to bend, at the cost of breaking, while resilience is the opposite.
Once the most admired value was stubborn, unyielding integrity; now we increasingly value the softer and more resilient (and sometimes more effective) quality of being able to adapt to adversity, to bend rather than break.

In ecology, an example is the response to fire: a resistant ecosystem will suffer little damage from a minor wildfire, while a resilient one will perhaps undergo more extensive damage, but it will be able to recover and return to its initial state even when the fire is much larger.

Equilibrium and adaptation, when an ecosystem is in balance

The concept of resilience is related to the concept of equilibrium. A resilient ecosystem is in a state of equilibrium. Just as a ball in a bowl, when moved to the side, quickly returns to its initial position, so is a resilient ecosystem able to restore its state of equilibrium following an event that has produced an alteration.

Of course, in complex systems, equilibrium does not mean immobility. In any ecosystem, everything is in constant motion. Single specimens – animals, plants and microorganisms – are born and grow, and perhaps move, while others die. But the overall structure remains unchanged and biodiversity is maintained: this is what’s meant by equilibrium.

The way an ecosystem reestablishes its equilibrium after a disturbance is adaptation.
After all, environmental adaptation is one of the drivers of evolution. For as long as life has existed on Earth, species have adapted to change. Thus ecosystems have evolved over very long time periods and have generally developed remarkable resilience, precisely because they have always had to cope with change.

The defining characteristics of resilient ecosystems

Certain properties of ecosystems render them particularly resilient.

First of all, biodiversity. If, for example, a lake is home to many species of fish, even the possible extinction of one species will not jeopardize all life in the ecosystem.
Similarly, if a forest is home to many species of trees with different abilities to tolerate water scarcity, the forest will be able to survive prolonged periods of drought.

One aspect of biodiversity is functional redundancy.
For example, pollination of flowers is carried out by many species of insects, but also by birds and other animals. Should one of these species fail, its role will continue to be carried out by the others.

An example of a highly resilient ecosystem is the Mediterranean maquis. Given its environmental and climatic conditions, it has always been subject to violent storms, fires and landslides. Over time, it has developed a remarkable capacity to recolonize damaged habitats, partly due to its rich biodiversity and functional diversity.

The importance of ecological resilience for environmental sustainability

Conversely, ecological resilience guarantees biodiversity. A resilient ecosystem offers many more opportunities for animal, plant or microbial species to become established or be reintroduced.

More generally, ecosystem resilience provides protection for the environment, and thus a safeguard for sustainability.
Consequently, it also contributes to the stability and security of human communities – all the more reason to reaffirm the concept of social-ecological resilience.

For example, fishing communities depend fundamentally on the health of the marine ecosystem for their livelihoods. Beekeepers need an ecosystem in balance for the well-being of insects and plants and in exchange, bees play a vital role in agriculture.

In addition to economic aspects, the health of ecosystems has an impact on the very safety of human populations. Forests, for example, protect mountain sides from landslides that could cause serious damage to settlements in the valleys below.

It’s not just a matter of safety: human health itself depends significantly on that of ecosystems. For example, an ecosystem resilient to climate change reduces the risk that some diseases (such as malaria) will extend their endemic range. 
Similarly, an ecosystem in balance lowers the likelihood of zoonoses – pathogens that make the species jump from animals to humans.

For all these reasons, ecological resilience is closely linked to environmental and social sustainability, and thus to the Sustainable Development Goals (SDGs) of the United Nations. This approach has also been embraced by the UN itself, in part encouraged by a study by the Stockholm Resilience Centre and by the International Council for Science (ICSU).

Strengthening ecological resilience and protecting the environment

Today, the environment is subject to new man-made threats, such as deforestation, intensive fishing, and above all, the climate crisis.
It is therefore crucial to protect and increase the socio-ecological resilience of ecosystems, especially those most at risk: while humanity has acquired enormous destructive power, it also has a unique capacity for reconstruction.

Initiatives and projects

Remediation efforts are targeted in several directions:

• restoring damaged ecosystems,
• adopting sustainable agricultural practices,
• of course, switching to low-impact technologies such as renewables or electric transportation.
  

Numerous initiatives for biodiversity and ecosystem health are being carried out by governments but also by large companies with awareness of the issue. The Enel Group adopted a biodiversity policy in 2015, which also included support for ecological resilience.

The 183 projects we’ve launched on four continents include ecosystem conservation, reintroduction of important species in terrestrial and marine environments, rehabilitation of natural habitats, and the ecological restoration of strategic or degraded ecosystems.

We give particular priority to reforestation projects, especially in some Latin American countries (including Brazil, Chile and Colombia). One of the most noteworthy involves the tropical dry forest of Colombia, an ecosystem rarer than the rainforest.

In other countries, projects have been organized in support of beekeeping (Italy, Spain, Greece and the United States), for the protection of bird life (Italy, Spain, Romania) and of marine fauna (Italy, Colombia).

These examples, along with all the others, cover very diverse areas, but are united by the nature-based approach they have in common: a model in which nature is our guide for all planned actions. But it is also a model inspired by resilience solutions that have proven successful because nature itself has been developing them over millions of years.