Status, trends and drivers of kelp forests in Europe: an expert assessment

Abstract

A comprehensive expert consultation was conducted in order to assess the status, trends and the most important drivers of change in the abundance and geographical distribution of kelp forests in European waters. This consultation included an on-line questionnaire, results from a workshop and data provided by a selected group of experts working on kelp forest mapping and eco-evolutionary research. Differences in status and trends according to geographical areas, species identity and small-scale variations within the same habitat where shown by assembling and mapping kelp distribution and trend data. Significant data gaps for some geographical regions, like the Mediterranean and the southern Iberian Peninsula, were also identified. The data used for this study confirmed a general trend with decreasing abundance of some native kelp species at their southern distributional range limits and increasing abundance in other parts of their distribution (Saccharina latissima and Saccorhiza polyschides). The expansion of the introduced species Undaria pinnatifida was also registered. Drivers of observed changes in kelp forests distribution and abundance were assessed using experts' opinions. Multiple possible drivers were identified, including global warming, sea urchin grazing, harvesting, pollution and fishing pressure, and their impact varied between geographical areas. Overall, the results highlight major threats for these ecosystems but also opportunities for conservation. Major requirements to ensure adequate protection of coastal kelp ecosystems along European coastlines are discussed, based on the local to regional gaps detected in the study.

Population genomics of the introduced and cultivated Pacific kelp Undaria pinnatifida: Marinas—not farms—drive regional connectivity and establishment in natural rocky reefs

“…These 25 localities, distributed across 12 bays, are representative of the present‐day distribution of U . pinnatifida in Brittany (Araújo et al., 2016; Epstein & Smale, 2017b). The sampling focused on neighbouring (i.e., occurring within the same bay) pairs of natural rocky reef and marina habitats whenever possible.…”

Biodiversity and ecosystem services in Nordic coastal ecosystems

“…The index consists of many different indicators ranging from richness of phytoplankton to abundance of harbor seals. A recent assessment of the status of kelp forests in European waters concluded that a general decrease in abundance of native kelp is apparent in some areas (partly in areas considered as southern distribution limits), while other areas have experienced increases (Araújo et al, 2016). Stocks of herring, cod and crab are reported to have declined in the last decade (Bakketeig et al, 2015;.…”

Biodiversity and ecosystem services in Nordic coastal ecosystems

“…This myriad of organisms provides essential ecosystem services such as fish biomass production, areas highly valued for recreation, along with carbon fixation and sequestration (Fig. 21) (Araujo et al, 2016;. Other Nordic key habitats include seagrass meadows, seaweed beds, mussel beds and soft sediment habitats.…”

“…A recent assessment of the status of kelp forests in European waters concluded that a general decrease in abundance of native kelp is apparent in some areas (partly in areas considered as southern distribution limits), while other areas have experienced increases (Araujo et al, 2016). The expanding kelp forests in Helgeland give hope for the future.…”