May 17, 2017 Biodiversity Written by Greentumble
What are indicators of ocean health
Any committed beach lover who enjoys

swimming in the sea will know this popular wisdom saying: “if you see sea urchins at the beach, then it means that the waters are very clean.” Regardless of the scientific validity of this claim, this highlights that we have been looking out for signs and metrics to evaluate how clean our seas and oceans are even before the advent of modern technology.

It is clear that if our oceans are healthy, marine life will be healthy and so we can enjoy eating fish and seafood. If our seas and beaches are clean, we can enjoy swimming in them. But how can we measure ocean health, when it occupies such a vast space of our planet and goes into great depths, some of which we have yet to explore?

Frightening discoveries

We often hear about researchers identifying chemical pollution in our seas with chemicals building up in mammals and other marine organisms.

A very recent example is the discovery that one of the UK’s last killer whales was contaminated with shocking levels of polychlorinated biphenyls (also known as PCBs), toxic chemicals which have been banned globally since the 1970s but are still found in the environment because they persist and accumulate in fat cells [1].

Lulu, as the animal was called, was found dead on the Isle of Tiree in Scotland last year after becoming entangled in fishing lines. Tests have recently proven that her body contained among the highest levels of PCBs ever recorded: they were 20 times higher than the safe level scientists expect cetaceans would be able to manage [1].

Other stories often reported by the media include the ever-decreasing yields of fish, ever increasing levels of marine litter (plastic litter is estimated to outnumber fish in the sea by 2050 unless we take action [2]) or the effects of climate change on unique ecosystems such as Australia’s Great Barrier Reef (Australia’s scientists discovered this year that another 8,000km had been damaged leaving the ecosystem in a “terminal state” [3]).

Alarming as this evidence is, it does not provide a holistic understanding of ocean health. This is important to have for several reasons:

    • to assess the state of our oceans;

    • to determine what metrics we should be focusing on to improve ocean health;

    • to measure progress and the impact of policies on improving ocean health.


Identifying indicators of ocean health

It is for those very important reasons that marine researchers from across the world worked hard to create an index that assesses overall ocean vitality [4].

The Ocean Health Index, as it is called, is made up of ten different measures that are aggregated into a single score which gives an indication as to how well our seas are doing. The metrics tracked assess features such as food provision, carbon storage, tourism value and biodiversity so that both the needs of humans and ecosystem sustainability can be reflected.

The index was completed in 2012 and it was the result of more than 65 scientists, economists and environmental managers working together and using information from over 120 scientific databases. Since then, more than 25 countries and regions have embarked on independent Ocean Health Assessments using the index [5].

Creating this index, however, was by no means straightforward. Jane Lubchenco, head of the US National Oceanic and Atmospheric Agency (NOAA) in the US, believes that the index is a great attempt at understanding what the trade-offs are for management decisions.

But there has been some criticism of the index, particularly insofar as the assessment of fisheries is concerned. The fisheries score is calculated as the difference between a region’s total landings and an estimate of maximum sustainable yield. For fisheries containing many species, 75% of the maximum sustainable yield was used.

The current state of the ocean health

In an initial assessment, our oceans scored an average 60 out of 100, which would indicate that there are some serious concerns regarding ocean health. What is more, almost one-third of the world’s countries scored below 50. Most recent data, the fifth assessment of the index, it seems that most scores have not changed much from 2012 to 2016 [6].

Specific metrics that are consistently scoring low are “tourism and recreation” which highlights that countries are not utilising in a sustainable way the benefits derived from a health tourism sector. In addition, the low scores of the metrics of “food provision” and “natural products” confirm that many regions are overfishing or are not using the full potential of the sea to produce more food sustainably. A key limitation of the index here is the issue of poor quality data or no data at all! This limits the ability of researchers to provide accurate estimates of the status of fish stocks and fisheries overall.

What is more, it is important to note that the index measures key metrics such as “biodiversity” and “coastal protection” based on data from the 1980s. Therefore, while biodiversity scored a high 91 points, this means that damage equivalent to 9 points was effected over the course of the last 30 years. The same applies for coastal protection which scored 87. This is an alarming trend – if we continue at this pace, by the end of the 21st century both these metrics will have decreased to a very concerning level [7].