Reconciling agricultural production with biodiversity conservation. Группа авторов
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, there is no information about their ecological quality. Protected habitats are monitored in the frame of the Habitats Directive (see Section 6) and the list of grassland habitats, though exhaustive, covers about 30% of EU grassland extent. The remaining 70% is described mostly in terms of geographical distribution and biomass production. Information on species is completely lacking.
Points were surveyed on a transect of 20 m × 2.5 m (Fig. 2), if they had at least 50% grassland coverage. Walking alongside the transect line, the surveyor should survey the vegetation of 1.25 m to the left and 1.25 m to the right. The starting point and the transect should be at least 5 m inside the grassland parcel, for the surveyed vegetation to be representative of the parcel and not of the edge. The transect should always originate from a LUCAS point, but the technical specifications contained information on how to reposition the transect if, given the starting point and the required orientation, it was not completely contained in the parcel.
Figure 2 Diagram of the theoretical location of the transect and the enlarged transect with respect to the LUCAS point (Eurostat 2018).
The timing of the survey was carefully planned, according to grassland phenology in the European Union. To allow the identification of the plants, the surveyor had to visit the site before the first cut or before the start of grazing. The surveys were therefore carried out following a latitudinal time gradient, from mid-April in Mediterranean South until mid-July in Boreal Scandinavia North.
The parameters list was the product of a consultation of EC services in need of information, to support environmental, agricultural and energy EU policies. The results of the consultation were translated into parameters to be surveyed.
These included information on:
• site characteristics (altitude, exposition, inclination, type of surface, moisture),
• a general description of vegetation (vigour, layers, presence of graminoids, forbs, woody plants layer, bare ground, age – older or younger than 5 years etc.),
• a more specific description of the flowering forbs (number of flowering forb species, flower density),
• identification of EUNIS habitat type (https://eunis.eea.europa.eu/about), and
• key species (plant indicator species) and structural plant species.
Concerning the last bullet point, 41 key species or key species groups were identified, and grouped in 10 lists with 20 species groups each for the different biogeographic zones characterizing the European Union. The revised list in the forthcoming surveys is reduced to 12 key species groups, identical for all the biogeographic zones, as this number was considered to be representative and suitable for non-botanist surveyors receiving a specific training to be able to recognize individual species. Such key species lists are assumed to be a direct indicator of the grasslands’ ecological quality. A grassland module is currently planned as part of LUCAS 2022, on 20000 points.
The raising awareness of the decline of insects (Hallmann et al., 2017; Sanchez-Bayo and Wyckhuys, 2019) and pollinators in particular (