6: Support nature’s resilience

How many punches can a person take before they fall? It depends on how much sleep they’ve had, what physical condition they are in, how hard the punches are, and a suite of other factors. Like people, we can and should do things that enable our ecosystems to take more punches, while trying to reduce the punches we deal it.

Genetic diversity in seagrass communities increases their ability to deal with stress. Photo: J. Nichols

A resilient ecosystem can rebound after a disturbance. Resilience is a measure of health and indicates how much stress a system can absorb before it permanently changes into an alternative state or collapses.

While resilience is essential in a healthy ecosystem, it is frequently ignored in conservation planning. This is because it is hard to measure, and often only recognized once the system is on the verge of collapse.

Biological communities have several natural attributes that make them resilient in the face of change and disturbance. For example, the presence of a keystone species determines persistence and stability and in the Salish Sea’s rocky intertidal zone: the sea star Pisaster ochraeus is essential to maintaining a highly diverse and stable community. In their absence, a monoculture of mussels occurs.

Other communities lacking a keystone species rely on a suite of interacting organisms to build resilience. Genetic diversity has also been shown to increase ecosystem resilience in seagrass communities stressed by elevated temperatures.

Human actions can inadvertently disrupt the factors that allow ecosystems to respond and persist in the face of change. Removal of a keystone species can lead to ecosystem collapse. Overfishing can have a detrimental impact on resilience: twenty years of data from reserve versus fished sites showed that reserves maintained a greater complement of species, and were consistently able to withstand and rebound from extreme, but not unusual, environmental conditions such as El Niño years. Fished sites had fewer species and communities and habitats within the fished sites frequently collapsed during El Niño events.

The principle of building ecosystem resilience is gaining ground. There is a complex systems approach for sustaining and repairing marine ecosystems, linking ecological resilience to governance structures, economics and society. Previously some scientists have found that corals in the Indo-Pacific and elsewhere are showing signs of resilience in their ability to adapt to climate change and called for international integration of management strategies that support reef resilience. Since then toolkits on effective ways to build reef resilience as an integral part of designing healthy marine ecosystems have been developed and are being applied worldwide on reefs from India to Africa, the Caribbean and the Americas.