Expansions of conservation areas such as the Natura 2000 network should be done in a way that improves not only area coverage but also representation (Visconti et al. 2019; Adams et al. 2021). The MTA indicator is one way of assessing the benefits of expansions using information of species distributions covered by conservation areas.
It can be interpreted as the average number of species or habitats that are adequately (indicated through a target) conserved by conservation areas (Natura 2000 and/or CDDA sites) within the European union.
The calculation of the MTA indicator (defined by Jantke et al. (2019) ) here uses EEA species and habitat reporting data and Natura 2000 information. For each 10 x 10 km grid id in the EEA Reference grid, we estimated the cumulative coverage of Natura 2000 sites per time frame, which we identified from the date SPAs, SCIs or SACs were designated or first added to the database. We then summarized per species or habitat the total distribution as well as the coverage of Natura 2000 sites within their distribution. See also the Section 2 section for a more detailed methodology breakdown.

The current calculation of the MTA is feasible every 6 years and can also be further refined to account for land-cover and land-use change, for example using data from the Corine Accounting layer. Furthermore, for comparability data on EEA reporting is used, although more higher resolved species distribution data (such as those produced by the NaturaConnect project) are slowly becoming available.

As data sources we relied for this demonstration on the officially used Article 12 (‘Birds directive’) and Article 17 (‘Habitats directive’) reporting data made by Member states (MS). Sensitive species were also included in those calculations and it is because of this reason that the input data can not be shared publicly.

As conservation areas we relied on the Natura2000 geopackage (last updated in April 2024).

Targets were calculated as log-linear targets (following (Rodrigues et al. 2004)) with a lower bound to 20% and upper bound to 90%. Different target formulations are feasible, for example those minimizing species-extinction risk (following (Jung et al. 2021)) and should ideally be based on a scientifically sound process at EU Member state level that takes into account ecological features and conservation needs.

It should be highlighted that the MTA is calculate based on the official Reporting by EU Memberstates as part of Article 12 and Article 17. Thus the targets, and conserved distribution and total distribution reflect the distribution of a species or habitat occurring in the European union only (despite some species likely also occurring elsewhere).

A more comprehensive version of the MTA will be calculated as part of the NaturaConnect project, which however does not use official European data, but specifically created data and targets for this purpose.