ECA_3.6_313;317

Knowledge gaps concern a) the full geographic (and temporal) coverage of past, current, and future trends of some ecosystem types and some taxa across Europe and Central Asia, b) patterns and underlying mechanisms of the biodiversity – ecosystem service relationship, and c) consideration of indigenous and local knowledge for all ecosystem types and taxa.
Geographic gaps: Overall, we found large gaps in knowledge on habitat extent and intactness, and species conservation status and trends for Eastern Europe and Central Asia. For instance, there is no systematic monitoring of plant and animal species across the range of these subregions. This is of particular concern given the size of these subregions and the diversity of habitat and species there. Outside the European Union long-term monitoring data is available almost exclusively for protected areas, which poses the risk of underestimating overall biodiversity trends in these regions.
Role of drivers: Information on future trends in biodiversity was predominantly focused on the impact of climate change, especially on plants and vertebrate species. There were very few studies investigating the impact of land-use change and even fewer investigating future projected impacts of pollution, invasive species, fishing and other drivers of change. It was often impossible to quantify the relative role of drivers of change in determining trends in species and ecosystems. This was due to lack of synthetic studies on this subject and the limited ability to meta-analyze the literature to provide this evidence. Therefore, the attribution of drivers to trends was based on the qualitative expert assessment of the authors rather than on quantitative empirical evidence from experimental or quasi-experimental studies.
Marine systems: Most marine systems are hidden to human eye and therefore lack of visibility, knowledge gaps, and lack of concerted actions are regularly pointed out for marine systems (e.g. Allison & Bassett, 2015; Mccauley et al., 2016). Nevertheless, the rate of description of new marine species has been increasing, since 1955, at a higher rate than for terrestrial species (Appeltans et al., 2012). Still, it is estimated that between one-third and two-thirds of marine species are still to be described, with estimates of the total number falling in the range of 0.7 to 1 million (as compared to the 226,000 species currently described). Under-estimation of marine diversity is not restricted to remote and under-studied locations. It also holds in Europe and Central Asia, with the increasing discovery of cryptic species (i.e. species that are not, or are hardly, distinguished according to morphological criteria). This underestimation of marine diversity implies that the trends are incomplete for most marine taxa.
An important gap in knowledge regarding current as well as future changes is genetic responses to environmental changes. Only few taxa, among them fishes and algae, have been studied so far (e.g. Araújo et al., 2016; Assis et al., 2016a; Hutchinson et al., 2003; Nicastro et al., 2013), but these studies indicate changes in genetic diversity and genetic structure of marine species. Integration of a genetic component is of paramount importance for conservation of genetic resources as well as for modelling of future trends in marine biodiversity (Arrieta et al., 2010; Gotelli & StantonGeddes, 2015).
Until recently, scant attention was paid to marine ecosystems and most marine taxa in conservation policies (e.g. see Habitats Directive and species lists in the European Union). Only a small number of species and few habitat types are included in Annex I of the Habitats Directive (EEA, 2015a). The gap in knowledge is exemplified by the large percentage of species in the “unknown” category in the first assessment of “good environmental status” in light of the newer Marine Strategy Framework Directive (2008) in the European Union (Figure 3.58). Most long-term marine datasets (since the 1950s) concern pelagic ecosystems (e.g. Beaugrand et al. 2002), intertidal rocky shores (e.g. Mieszkowska et al., 2006), or specific taxa or taxonomic groups (in particular fishes, marine mammals or seabirds). Almost no data are available to document changes in subtidal rocky areas although they are rich in biodiversity and support key engineer species, for instance in subtidal kelp forests (Smale et al., 2013).
Open ocean plankton communities are also poorly known. It is estimated that, in each litre of seawater, there are on average 10 billion organisms, including viruses, prokaryotes, unicellular eukaryotes, and metazoans.
The most notable knowledge gap in marine biodiversity for Europe and Central Asia is the lack of data on status and trends of biodiversity in deep-sea areas (>200 m) despite canyons, seamounts and other important deep-sea habitats and ecosystems being present in Europe and Central Asia Seas and Oceans. Less than 1% of the deep-sea floor (UNEP, 2007; Rogers et al., 2015) and 0.4-4% of known seamounts (Kvile et al., 2014) have been sampled. Those that are known are mainly areas with sandy bottoms that can be trawled. This highlights significant gaps in basic knowledge, including lack of baseline data on biodiversity, abundance and biomass and its spatial and temporal variations. New habitat types and species are still being discovered on almost every deep-sea scientific cruise
Some progress in addressing these knowledge gaps is signified by recent marine assessments. For instance, an assessment of data available and surveys needed was recently reviewed for kelp in the North East Atlantic (Araújo et al., 2016). The results from Tara Oceans and Malespina cruises and Ocean Sampling Day program, which collected genetic, morphological, and physico-chemical samples from stations around the world (about 35,000 biological samples and about 13,000 contextual measure taken a three different depths just for Tara Oceans) is now being analysed by a large international team of scientists. Metagenomes and meta-barcodes from stations are being built as well as quantitative and high-resolution image databases, and the first global studies are being published (e.g TARA Ocean (https://www.embl.de/tara-oceans/start/). IUCN recently coordinated an assessment dedicated to the Anthozoans of the Mediterranean Sea, which include, for instance, iconic species like the red coral (Otero et al., 2017).
Freshwater systems: The chemical status of 40% of Europe’s surface waters remains unknown (EEA, 2015d), considering that good chemical status was only achieved for all surface bodies in five of the 27 European Union member States, it is likely that the environmental conditions of some of these water bodies are poor.
Agricultural areas: Overall information on biodiversity trends in agricultural areas decreases from west to east. In particular, studies on biodiversity and agriculture for Eastern Europe and Central Asia often focus on drivers of biodiversity in agricultural areas rather than biodiversity trends (Smelansky, 2003), while biodiversity is surveyed for semi-natural ecosystems rather than more productive agroecosystems in these countries. Capacity building for monitoring biodiversity in agricultural areas in the eastern part of the region is thus needed.
The level of knowledge on biodiversity trends in agricultural areas and main direct drivers has increased substantially during the last decade. However, most studies have used species richness or abundance (and genetic diversity for animal breeds and plant varieties) as indicators of biodiversity. Promoting a stronger focus on functional diversity in future studies and monitoring schemes may be the best way to complement previous approaches. To better understand and predict biodiversity trends in agricultural areas in Europe and Central Asia, it will be necessary: (i) to reinforce the knowledge basis on the demography and population dynamics of species (including the role of behaviour, density-dependent effects, and extinction debt); (ii) to account for small-scale spatio-temporal effects and scale up biodiversity changes and trends from local to national and regional levels; and (iii) to detail the effects of changes in agricultural practices (characteristics of the varieties grown, harvesting techniques, types of pesticides used, etc.) to a greater extent (Kleijn et al., 2011).
Urban areas: The data available for urban areas are mostly for the larger and more easily observed taxa, such as vascular plants, birds and mammals. There is good data for bats, and reasonably good data on amphibians, reptiles and some insect taxa, including butterflies. The small amount of data available on taxa more difficult to observe and distinguish, such as Syrphids and other Diptera, suggest high levels of diversity and numerous rare and threatened species (Kelcey, 2015). Thus, more surveying of such taxa would generate valuable new knowledge on urban biodiversity.
Taxonomic gaps: While birds are arguably the most studied and best known group in Europe and Central Asia, there is still one species, the large-billed reed-warbler, Acrocephalus orinus listed as being data deficient by the IUCN and therefore having unknown extinction risk, and there are also 79 species with unknown population trends in the European Union (EEA, 2015a). Long-term trends are rarely available. Low capacity or difficult access means that regions such as Caucasus, the Arctic part of Europe, Romania, Croatia, the Faroe Islands and the Azores are underrepresented in bird conservation status assessments (BirdLife International, 2015).
More substantial knowledge gaps exist for other terrestrial vertebrate groups. There are, respectively, 55 mammals, 11 reptiles and three amphibians that are classified as data deficient by the IUCN. In addition, population trends are unknown for 100 of 1,026 bird species extant in the region and assessed by IUCN as well as 263 of 537 mammals, 7 of 129 amphibians and 56 of the 268 species of reptiles (IUCN, 2017c).
There are at least 100,000 species of insects known in Europe, and an unknown number of earthworms, arachnids, snails and other invertebrate species. However, it is plausible that several hundreds of thousands of species of invertebrates occur in Europe and Central Asia. Despite this extremely high diversity, and importance for ecosystem services, only a very small proportion is listed in the IUCN Red List. More specifically, there are only 2,132 species of terrestrial invertebrates in the IUCN Red List that are extant in the Europe and Central Asia region. The majority of these are European bees, which include 1,965 species (Nieto et al., 2014). Moreover, almost nothing is known about species, trends and threats for this taxonomic group from Central Asia.
There are no meaningful trends in geographic extent or population size of freshwater species available for Europe and Central Asia. Therefore, a table of trends and importance of drivers was impossible to produce. Of particular concern is the lack of data for freshwater invertebrates, for which even current status is available only for a minority of species (EEA, 2010). For example, several freshwater crab species have data deficient status according to the IUCN Red List, which highlights the need to increase monitoring efforts globally but also in Europe and Central Asia.
Similarly, almost a quarter of all European freshwater molluscs are data deficient and many might prove to be threatened once enough data become available to evaluate their extinction risk. However, the number of data-deficient species may well increase, since 76% of freshwater fishes and 83% of freshwater molluscs have unknown population trends (Cuttelod et al., 2011). Data are also deficient for many other freshwater invertebrate groups (Balian et al., 2008). This is owing to several reasons such as lack of taxonomic information, knowledge gaps in geographical coverage of data and lack of long-term data. These gaps need to be assessed urgently, by fostering taxonomic research and monitoring and by making proprietary databases and databases under pay-wall freely and openly available.
Biases across taxonomic groups in marine systems are also largely documented (McCauley et al., 2015; Poloczanska et al., 2013) (Figure 3.59). For instance, no extinction of marine animal species has been documented in the past five decades (IUCN, 2017b), but only a small fraction of described marine mammals has been evaluated and 17 that were assessed were determined to be data deficient (IUCN, 2017c; McCauley et al., 2015). This is exemplified by the extensive work carried out by Brooks et al. (2016) in which marine taxa are not included, except for decapods. This is not surprising, since trend data are not available even for 69% of the best-known group of marine organisms, the European marine fish species.
Availability of regional information on marine plankton and invertebrates is varied across Europe and Central Asia, with certain systems having more information on biodiversity status available (e.g. the North East Atlantic (OSPAR, 2017); the Mediterranean (Coll et al., 2010a); and the Baltic (Ojaveer et al., 2010). Most often, information remains descriptive: existence, abundance, geographical distributions of species for instance, but little metainformation is available yet to discern conservation status. OSPAR (2008) lists five marine invertebrate species as threatened or declining in the North Atlantic and North Sea since 2003, as well as a series of habitats formed by marine invertebrates (e.g. mussel beds, deep sea sponge aggregations). In the Mediterranean, while much information is available, marine invertebrate knowledge is often considered to be limited, with new species still being described. There is also a high proportion of endemic species in the Mediterranean, especially sponges and mysids (Coll et al., 2010a). Mediterranean anthozoans have been reviewed in detail by IUCN, showing that 13% of them are threatened while almost half lack sufficient data for assessing risk of extinction (Otero et al., 2017).
Marine microbes may represent more than 90% of the ocean’s biomass, are the major drivers of its biogeochemical cycles (Danovaro et al., 2017), and can be found in the whole water column up to 2,000 metres below the seafloor. Although there has been an exponential increase in research on marine archaea, bacteria and viruses, and evidence that archaea and viruses may increase in importance with depth (Danovaro et al., 2015) their biodiversity and functioning is still largely unknown.
At least 7,000 species of lichens are known to occur in Europe (excluding Russia), while across the whole of Europe and Central Asia only five lichen species have been assessed in the IUCN Red List and have known conservation status (IUCN, 2017b).
Less than 10% of all species of vascular plants known to occur in the region have been assessed by the IUCN Red List (2,483 species for an estimated >30,000 for the region) (IUCN, 2017c). Among those assessed, 46.2% have unknown population trends. These also include species of conservation concern, such as 20% of the species included in the European Red List of Vascular Plants; (Bilz et al., 2011). These knowledge gaps are caused by lack of field data, difficulties in accessing data for some countries, and uncertain taxonomy. Processes threatening vascular plants are also unknown for several species. The number of fungus species in Europe exceeds 75,000, 15,000 of which are macrofungi (Senn-irlet et al., 2007). Currently there are no regional or continental data on status and trends of fungi.
We were unable to assess status and trends in diversity, biomass and community composition of soil and freshwater micro-organisms: Protozoa, Bacteria, Rotifera, Nematoda, Tardigrada, despite the key role of these organisms in soil formation, nutrient and carbon cycling, and water retention (Orgiazzi et al., 2016).
Relationship between biodiversity and ecosystem function and services : For some ecosystem services, there is insufficient data to evaluate the relationship between biodiversity and ecosystem service provision. For example, the effects of fish diversity on fisheries yield and the effects of biodiversity on flood regulation are inconclusive (Cardinale et al., 2012). Additionally, ecosystem services provided by taxa other than plants are only beginning to be studied. Finally, the majority of studies reviewed focused on taxonomic diversity at the community level (i.e. species richness or diversity), rather than on intraspecific, functional phylogenetic diversity.