C3: Diverse seas: status of marine mammals and marine birds

Interim Interim

Short description

This indicator of diverse seas tracks changes in status assessments of marine mammals and marine birds. The assessments of marine mammals will be based on trends in the abundance of harbour seals; Atlantic grey seal pup production; and the abundance of cetaceans (whales and dolphins). The assessments of marine birds will be based on the proportion of breeding seabirds and wintering waterbirds that have met abundance targets, which were set to inform progress towards Good Environmental Status (GES). The GES assessments of marine mammals and birds were used in the updated UK Marine Strategy (UKMS) Part One (2019) and to fulfil reporting commitments under the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR).

This indicator is not available for reporting in 2021 in a finalised form as some further development is being undertaken. An interim indicator is presented here that shows (a) changes in the abundance of harbour seals and the production of Atlantic grey seal pups in the north-east and south-east of England, and (b) changes in the abundance of breeding seabirds and wintering waterbirds in the Greater North Sea and Celtic Seas (OSPAR marine regions including data from neighbouring countries). The assessments of seals and marine birds used for this interim indicator have been reported at a UK scale under the updated UKMS Part One (2019). The assessment for seals used data from 1994 to 2014, the most recent data on seals presented in the charts below are published by the Special Committee on Seals (SCOS). The indicator will be kept under review during the development of ‘D5 Conservation status of our native species’ as some elements of this indicator may ultimately be included in D5 instead. Cetaceans are not yet included in this indicator, but they will be once more definitive assessments can be made. Whale and dolphin species were assessed in the UKMS Part One (2019) using data on abundance. However, for most species, trends in abundance could not be determined because there were an insufficient number of population estimates.

Note

While the data currently available for breeding seabirds and wintering waterbirds in this interim indicator predate the 25 Year Environment Plan, they provide the most recently available assessment of changes in GES of seals and marine birds. They enable a better understanding of a baseline from which to measure progress towards the goals of the 25 Year Environment Plan when the indicator is next updated.

Trends in harbour seal abundance are derived from counts of seals on land in August of each year when they are moulting; Atlantic grey seal status is assessed using counts of pups that estimate pup production at major breading sites. Targets for GES were met if harbour seal abundance and Atlantic grey seal pup production: a) declined by less than an average of 1% per year during 2009 to 2014, or b) decreased by less than 25% since the baseline year (1992 or start of time series, if later). The UKMS Part One (2019) GES assessment for seals covered the Celtic Seas and Greater North Sea.

GES is achieved for breeding seabirds and wintering waterbirds if 75% or more species meet or exceed their thresholds for relative abundance (the dashed horizontal line on Figure C3b). The relative abundance of a species is the annual abundance expressed as a proportion of the baseline, which was taken as the abundance at the start of the timeseries in 1992. Thresholds for relative abundance were set to define GES: greater than 80% of the baseline for species that lay one egg and greater than 70% of the baseline for species that lay more than one egg.

Trend description

a) Seals

Trends in harbour seal numbers in eastern England have been largely positive since the mid-1990s, although they appear to have levelled off and then fallen between 2015 and 2019. In the south-east, where the majority of the England population are found, numbers have fluctuated showing an increase from 2,793 in 1995 to 4,944 in 2018 followed by a sharp decline to 3,752 in 2019. Numbers are much lower in north-east England; they have shown a steady increase from 45 animals in 1994 to 91 in 2015 before declining to 79 in 2019. The UKMS Part One (2019) assessment based on the period 1994 to 2014 concluded that because of declines in Scotland, GES had not been achieved for harbour seal abundance in the UK Greater North Sea sub-region (which includes seal populations in the north-east and south-east England). In south-east England annual Atlantic grey seal pup production has risen exponentially from just 200 pups in 1992 to 7,902 pups in 2019. In north-east England the rise in pup production has been steadier, from 985 pups in 1992 to 2,823 in 2019. The UKMS Part One (2019) assessment based on the period 1992 to 2014 concluded that GES for Atlantic grey seals has been achieved in the Greater North Sea.

b) Marine birds

The proportion of seabird species meeting thresholds for breeding abundance in the Greater North Sea and Celtic Seas has remained stable since 2012 but remains below the 75% target (59% in the Greater North Sea in 2014 and 63% in the Celtic Seas in 2015). The UKMS (2019) assessment concluded GES for breeding seabirds has not been achieved in the Greater North Sea or Celtic Seas. The proportion of wintering waterbird species meeting thresholds for non-breeding abundance in the Greater North Sea has declined sharply, but is still on target (78% in 2013/14); the proportion of wintering waterbird species meeting thresholds in the Celtic Seas has also declined sharply (53% in 2014/15) and has remained below target since 2006. GES for non-breeding (wintering) waterbirds has been achieved in the Greater North Sea but not in the Celtic Seas.

Sub-categories

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This table provides metadata for the interim or final indicator presented above.

Indicator name

Diverse seas: status of marine mammals and marine birds

Indicator reference

C3

Outcome Indicator Framework theme

Seas and Estuaries

Headline indicator status

Diversity of our seas

Relevant goal(s) in the 25 Year Environment Plan
  • Thriving plants and wildlife
Relevant target(s) in the 25 Year Environment Plan
  • Reversing the loss of marine biodiversity and, where practicable, restoring it
  • Ensuring seafloor habitats are productive and sufficiently extensive to support healthy, sustainable ecosystems
Position in the natural capital framework
  • Condition of assets - seas
Related reporting commitments
  • UK Marine Strategy (Marine Strategy Regulations 2010)
  • Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR)
  • Berne Convention
  • Convention on Biological Diversity Targets
  • Relevant to Sustainable Development Goal 14
Geographic scope

Seals – England; Marine Birds – OSPAR marine regions (Greater North Sea and Celtic Seas)

Status of indicator development

Interim

Date last updated

11 June 2021