Of the monitoring initiatives presented in this paper, this is the only one that has a wall-to-wall coverage of the European Union, with a sampling density sufficient to derive statistically meaningful information at different scales (EU, national, regional), on different ecosystem types (farmland, forest; montane birds and mire birds for North Europe indicators are under development) or climate change (Gregory et al., 2009).
The information is valuable and widely used, since it is considered that, being at the top of the food chain, birds are indicators of the environment’s health. The farmland bird indicator is to date the most widespread biodiversity indicator used in EU policies (impact indicator of the CAP8; condition indicator of the Monitoring and Assessment of Ecosystems and their Services – MAES9), indicator frameworks (Streamlining European Biodiversity Indicators – SEBI10; agri-environmental indicators – AEIs11; OECD agri-environmental indicators12) and global assessments (e.g. FAO, 2019).
2.2 European breeding bird atlas
The EBCC has organized a second European Breeding Bird Atlas (EBBA2). This project, complementary to the PECBMS, brings information on spatial distribution and abundance of all bird species in Europe including European Russia and Turkey (www.ebba2.info). The outputs of the project which has collected field data from 2013 to 2017 are the maps of distribution and abundance of each species in a grid of 50 km×50 km, and maps of modelled probability of occurrence of selected species in a grid of 10 km×10 km. The atlas also provides maps of change in distribution in comparison with the 1980s, when the first atlas was produced. Information about the spatial distribution of species has been shown to have an extremely high value for policy, nature conservation and research (Herrando et al., 2019). The EBBA2 outputs will be published in 2020.
2.3 Butterflies
The experience of bird monitoring has paved the way to other initiatives aimed at planning and putting in place large-scale surveys. One of these is butterfly monitoring. Butterfly populations are in fact highly sensitive to environmental change, providing an early warning of impacts on ecosystems. Moreover, being insects, they are part of the food chain and they are also important pollinators. The process of establishing monitoring schemes in EU countries and improving the Grassland Butterfly Index is very similar to the PECBMS experience. Some countries had developed their own Butterfly Monitoring Scheme already in the nineties (e.g. Belgium – Flanders, the Netherlands, Finland, Spain – Catalonia), with the United Kingdom at the forefront, having started its monitoring activities in 1976 (Brereton et al., 2009).
Butterflies are counted along line transects, by experts or skilled volunteers. The counts take place several times a year (in the majority of cases 10–20 times), under well-defined weather conditions and times of the day. Transects are distributed either following a statistical procedure for random selection, but in the majority of cases are free choice of volunteers (Brereton et al., 2009). A transect is on average 1 km long, and it may intersect one habitat type or more. The surveyor should walk the transect every week during the butterfly season, counting the individuals seen within an imaginary box of 5 m wide, 5 m high and 5 m ahead of the observer (Sevilleja et al., 2019).
The early 2000s were a topical moment for butterfly monitoring: van Swaay et al. (2006) associated butterfly species to biotopes, highlighting the importance of grasslands, in particular dry grasslands, as the most species-rich biotopes, but at the same time as the biotopes hosting the largest numbers of threatened species. Van Swaay and van Strien (2005) proposed the development of a European grassland butterfly indicator, which followed the protocol of the European common bird indicator (Gregory et al., 2005) and made use of the same TRIM programme to calculate national indices. Finally, Butterfly Conservation Europe was founded, to coordinate monitoring efforts and support national offices in setting up their monitoring schemes (van Swaay et al., 2006).
Through the years that followed, more countries initiated a monitoring scheme, and the European Grassland Butterfly Indicator was updated every two years from 2008 onwards (EEA, 2013a; Van Swaay et al., 2019).
More recently, the European Commission has launched a pilot project (Assessing ButterFlies in Europe – ABLE) to increase the number of monitored countries, expanding the surveys in particular in South and East of the European Union, to have a more representative index. Moreover, ABLE is meant to develop indices for other habitat types besides grasslands, and to support the monitoring network through online resources. The initial period of funding is two years (until November 2020), and the partnership is composed of Butterfly Conservation Europe, the Centre for Ecology and Hydrology (UK), the Helmholtz Centre for Environmental Research (Germany), Dutch Butterfly Conservation (the Netherlands) and Butterfly Conservation (UK) (more information available at www.butterfly-monitoring.net).
In 2018 the first pilot of a EU-wide grassland survey was carried out in the frame of the Land Use/Cover Area-Frame Survey (LUCAS). LUCAS is a harmonized land cover and land-use data collection exercise that extends over the whole of the EU’s territory. Data are gathered through direct observations made by surveyors on the ground or through photo-interpretation, aimed primarily at collecting information on land use and land cover. The whole LUCAS 2018 survey was based on 337 854 points/observations, of which 238 077 were in-field and 99 777 photo-interpreted (EUROSTAT, 2019).
The survey started in 2009 and through the years different modules were plugged-in to exploit the LUCAS infrastructure and collect data on relevant environmental variables. Two of the modules cover grasslands and soils (for the latter see Section 5).
During spring/summer 2018, 2173 grassland points were surveyed in 26 countries for a total of 134 surveyors involved. In parallel, 36 expert botanists visited a subsample of 730 points, and their data served as control points to evaluate the reliability of the survey (Sutcliffe et al., 2019) (Fig. 1). The points were selected among those that in the previous survey LUCAS 2015 were identified as grasslands, and their distribution is statistically significant at the level of environmental zones.
Figure 1 Expert botanists (a, c) and corresponding surveyors (b, d) transects. © European Union, LUCAS 2018.
The reason for having a grassland survey derives from the awareness that most EU grasslands are not described in any database to a degree that may be used in the policy process. For example,
