Scotland's seas: towards understanding their state

Executive Summary

Developing Scotland's Seas: Towards Understanding their State is a key first step to taking forward the recommendations from the Advisory Group on Marine and Coastal Strategy and the Environment and Rural Development Committee, as well as establishing a baseline against which future marine and coastal policy can be measured. It is a step towards achieving the Scottish Government's vision for seas that are "clean, healthy, safe, productive and biologically diverse" and that are "managed to meet the long term needs of nature and people". This is an interim report that will be followed by a more comprehensive review, the State of Scotland's Seas, in 2010.

The Scottish Government's vision is supported by a broad range of legislative and obligatory drivers. At the international level these include OSPAR, which covers the north-east Atlantic, and several European directives, including the Marine Strategy Framework Directive, the Water Framework Directive and the Habitats and Birds Directives. The European policy agenda is aimed at achieving and maintaining "good environmental" or "good ecological" status because there is recognition that the environment and its ecological structure and function need to be maintained if they are to remain economically productive and capable of supporting the health and wellbeing of people. This is being translated into domestic policy through the Government's vision and domestic legislation.

The nature of Scotland's seas owes much to its location at the edge of a continental shelf where water depth plummets from 250 m to oceanic depths of greater than 2,000 m. The warm oceanic waters from the south-west keep Scotland's climate temperate. In addition, they provide a supply of nutrients required for the photosynthetic fixation of carbon thereby maintaining the intricate food chain, and in turn, the seas rich biological diversity.

The Scottish coastline supports much economic and recreational activity. For example, the coastal waters have important potential for renewable energy generation, while the relatively shallow waters of the North Sea are where much of the oil and gas is currently extracted. Scottish ports handle large quantities of crude oil, coal and other 'dry bulk' products as well as providing the embarkation point for over 10 million passengers peryear.

Evidence for the state of Scotland's seas comes from a number of indicators and many sources. The organisations with executive responsibility for the collation, stewardship and reporting of data are Fisheries Research Services, the Scottish Environment Protection Agency and Scottish Natural Heritage. Scotland has a long tradition of marine research and various other organisations, including some from outside Scotland, also provide information to underpin interpretation. Data sets that reflect the physical and biological state of Scotland's seas, and other reports derived from these data, have been listed in annexes to this report.

The ocean climate around Scotland is changing in a way that will lead to changes of the distribution and abundance of marine species, and may also lead to changes in the coastline, storminess of the seas and wave heights. Water temperature is increasing at a rate of 0.2-0.4ºC per decade and is following similar trends to the wider North Sea and North Atlantic. Thermal expansion of the oceans and melting glacier ice is leading to sea-level rise. Although rates of sea-level rise are variable, 12% of Scotland's coastline is already subject to erosion and this is likely to increase in future. A long-term increase in salinity is being observed while acidification of the seas, because of increased dissolved carbon dioxide, presents a particular challenge to marine organisms.

Clean and safe seas

There is a strong interaction between the energy within coastal seas, in the form of waves, tides and currents, and the processes of erosion and sedimentation. Sediments are derived from land and coastal erosion and many settle in relatively low energy regions. The result is a patchwork of seabed sediments and some of these areas, such as the Fladen Ground, can be productive for fisheries. These sediments store pollutants that could enter the human food chain, although monitoring has shown a reduction in most pollutant burdens over the past 20 years.

There is a general reduction in contaminant levels in estuarine sediments because regulation has led to declines in the discharges of metals and organic pollutants from rivers. Nevertheless, some historically polluted areas remain and particular attention must be given to an ever increasing number of synthetic substances that are entering the marine food chain, as they may affect biota in subtle but potentially damaging ways. The amount of nitrogen entering the sea, mainly derived from agriculture, has not declined although at present there appear only to be local effects of this in some of the smaller east coast river estuaries. Toxic algal blooms, which can affect shellfish fisheries and other marine wildlife, do not appear to have a simple cause and there is currently little evidence that they are caused by pollution. Marine litter continues to be a problem on many beaches and this can be a hazard to wildlife. Improved sewage treatment and more appropriate location of discharges has greatly reduced the bacterial contamination of beaches in the past 10 years though again run-off from diffuse agricultural and urban sources still needs more management. Radioactive discharges, marine noise, and discharges of warm water also have effects though generally only local in nature.

Healthy and biologically diverse seas

Phytoplankton communities are the fundamental basis of marine food chains. New primary production is often focused in regions where rivers deliver nutrients to the sea but in Scottish waters many of the nutrients come from inflow of oceanic water from the Atlantic. This makes Scotland's seas relatively rich in primary production and leads to the richness of marine fish populations. Overall, the primary production of Scotland's seas is in a favourable state but recently there have been major shifts in the distribution of the zooplankton that feed on phytoplankton. Warmer water species have increased and colder water species have declined. The overall effect that this could have on food chains is not known and, as a result, some suggest that the changes in zooplankton populations may be a cause for concern. What effect this will have on the Scottish seas' species of plants and animals (about 6,500, increasing to 40,000 if microbial flora are included) is not known.

Scotland has some of the finest marine habitats in Europe, some of which are very fragile. Although our knowledge of these is improving, many parts of Scotland's seas remain unexplored and it is possible that some of these fragile communities will be damaged or lost before there is any knowledge of their existence. Of the 17 Scottish biodiversity state indicators that have been identified, five are of particular relevance to the marine environment. These help to provide an overview of the health of Scotland's seas. To date, 34 Special Areas of Conservation have been designated in Scotland's seas covering seven different habitat types (56 features) and three species. A recent assessment showed that 97% of features surveyed within these sites were in favourable condition. Further protection has been provided for those sites found not to be in a favourable condition but it may take many decades, even centuries, for full recovery in some cases.

Productive seas

Government statistics attribute £2.2 billion of marine related industry activity (excluding oil and gas) to the Scottish economy and about 50,000 jobs. Nevertheless, it is difficult to estimate the overall contribution that the sea makes to the Scottish economy or whether this potential is being fully utilised. However, it is clear that the seas provide a basis for a broad range of important industries. More than 99% of UK marine aquaculture is based in Scotland and there are plans to further increase production. Although some wild finfish stocks are not as productive as they might be, shellfish stocks are overall in good condition. Oil and gas extraction continues to make a major economic contribution (estimated at about £20 billion additional Gross Domestic Product in 2005) with relatively low environmental impacts. Marine renewable energy is likely to become a major new product from Scotland's seas, although there is uncertainty about its environmental impacts.

Next Steps

The next stage in this ongoing process will be to produce the State of Scotland's Seas report in 2010. As part of the process there is a need to improve the coordination of marine science with active industry involvement. There is also a need to develop a greater range of marine indicators which must take account of the multiple impacts to which any sea area is exposed. Finally there is a need to respond to the demands of the European Marine Strategy Framework Directive.

Ensuring that Scottish seas are used in a sustainable manner requires good management underpinned by high quality scientific research and monitoring. This will make certain that, for future generations, Scotland's seas will be clean, safe, healthy, productive and biologically diverse.

The authors welcome feedback on this report and encourage the completion of the short questionnaire at the back of the report. Alternatively comments can be sent to StateofScotlandsSeas2010@scotland.gsi.gov.uk.