June 8th was World Oceans Day - a day to honor the blue planet and what it means for us humans. As a way to highlight this event at the Stockholm Resilience Centre, I was asked to briefly say something about why we should preserve the world's oceans and why resilience thinking has a role to play.

1. Why do oceans matter?

Oceans and major seas cover 70% of the Earth and provide a strong flow of goods and services upon which human societies and economies depend on. Some of these ecosystem services (the benefits people obtain from marine ecosystems) are relatively easy to put a number on. For example, fish captured from the oceans have an estimated economic value of over $80 billion. Marine tourism, often concentrated to coastal marine areas such as coral reefs, generates approximately $200 billion annually. Fisheries and fish products provide direct employment to nearly 27 million people and more than a billion people rely on fish as their main or sole source of animal protein, especially in developing countries.

There are other ecosystems services that are equally important, but more diffuse and difficult to measure and quantify. For example, in many cases the practice of fishing is hugely important to the cultural identity of many coastal communities. In some parts of the world certain fish species are at the base of many coastal communities culture, e.g. Pacific Salmon and many First Nations in eastern Canada.

Ofcourse, by covering such a substantial proportion of the Earths surface results in the oceans playing a critical role in the major nutrient cycles of the biosphere. For example, in the context of ongoing climate change it is important to highlight that oceans have absorbed almost 25% of all CO2 emissions since pre-industrial times. Models project that this carbon sink function will be jeopardized by the combined effects of global warming and changes in oceanic circulation patterns.

The main drivers altering and strangling the flows of goods and services from marine ecosystems are human activities such as overfishing, climate change and eutrophication (mainly as a result of poor agricultural practices). Protected areas cannot do much against climate change but they can help rebuild overfished fish stocks and maintain biodiversity. Maintaining biodiversity can help build resilience, i.e. buffer marine systems from human disturbances, of the ecosystems that fisheries rely on.

However, protected areas are not a cure-all medicine. They will work in some contexts and situations but not in others. In developing countries, for example, protected areas might fail in their goals simply because people need to continue fishing these areas to survive and developing nations have little capacity to enforce the boundaries of the protected areas. Succesfully confronting the marine crisis requires a battery of complementary approaches to management that are tuned to the local context of the fisheries.

Resilience theory has contributed heavily in helping us understand the behaviour of marine ecosystems in response to human actions and disturbance. When marine ecosystems are heavily exposed to human actions the ecosystem can change abrubtly and substantially. For example, parts of the North Pacific have gone from a fish-dominated regime to one dominated by jellyfish. Similarly, and also as a response to overfishing, Jamaican coral reefs have become dominated by thick seaweeds. Resilience theory has helped prescribe management schemes to avoid these shifts.

Resilience specifically highlights the importance of key processes undertaken by crucial functional groups. Functional groups are groups of species performing similar things in the ecosystem (i.e eating seaweeds, eating jellyfish larvae and other plankton, burrowing in the bottom sediments). Having many species within each of these fucntional groups adds resilience to the systems. Equally importantly is that these species exhibit differences in their response to environmental change, so that when environmental conditions change some species within a functional group will remain abundant.

The concept of resilience has also been pivotal in developing the theory of social-ecological systems (SES’s; interdependent and linked complex systems of people and nature). There is now an increased recognition that along with understanding the ecological aspects of marine social-ecological resilience, we need to dig deeper into its broad social, institutional and economic dimensions.