National ecosystem services assessment in Slovakia – meeting old liabilities and introducing new methods

This article provides an overview and results of the pilot national ecosystem services assessment in Slovakia. It follows the MAES process and past ecosystem services (ES) research in Slovakia and is based on original research methodology using spatial and statistical data. The initial step of national ES assessment resulted in the selection of significant ES for the evaluation process, where 18 ES in three groups were selected (five provisioning, 10 regulatory/maintenance and three cultural ES). An original assessment model provided the theoretical and methodological framework for national ES evaluation. The principal result is an assessment of the national landscape’s capacity for ES provision, based on evaluation of the landscape units and selected properties and indicators at the ecosystem level. These inputs included habitat types and watersheds, administrative units, ‡ ‡,§,| § § |,¶


Introduction
Although the ecosystem services (ES) concept was introduced in the early 1980, it has received most attention within the last twenty years. The ES issue progressively interweaves various fields of the natural sciences and touches on practical and political areas as well and, although it is gradually incorporating considerations of global economics, its level of practical application remains insufficient (Costanza et al. 2017).
The basic definition states that "ecosystem services include all direct and indirect contributions of ecosystems to human well-being" (TEEB 2010). Authors such as de Groot et al. (2010) argue that the concept of ES and their assessment enables a better understanding of the ecological, social and economic benefits of the sustainable use and protection of ecosystems. The methods of bringing this about include ES mapping, assessment, quantification and further interpretation (Burkhard and Maes 2017). There is a wide range of ranking schemes, indicators and quantification methods, including spatial localisation (Burkhard et al. 2014), but the most frequently used and recommended ES assessment methods combine the biophysical, socio-cultural and economic fields. In addition, a broad consensus in the scientific community for the need to link different ES assessment methods has led to the development of integrated assessment methods (Dunford et al. 2018).
The mapping and assessment of ecosystems and ecosystem services (MAES) process in the EU countries (BISE 2019) aims at the ES valuation and implementation, mainly at the national level. National ES assessment studies have gradually developed since 2010-Schröter et al. (2016, Nedkov et al. (2018) have recently analysed the state of ES mapping in European countries. In 2019, the overall level of implementation of MAES commitments reached 70%. Full implementation means mapping and assessment of the state of ecosystems and ES, economic valuation of ES and integration of the ES within national policies. The United Kingdom, the Netherlands, Ireland, Finland and Bulgaria have already achieved full implementation and Italy, Romania and France are making significant progress towards this objective. Besides these countries, Greece, Estonia and Slovenia have made the most significant progress since 2015 (BISE 2019).
Slovakia created a MAES expert working group of representatives from various governing and administration institutions and academia in 2014, to map and assess ecosystems and their services. The Ministry of the Environment also prepared two strategic policy frameworks at the national level. In 2014, "Biodiversity Protection Strategy for 2012-2020" set targets for 2020, highlighting the preservation and enhancement of ecosystems and their services through the establishment of green infrastructure and the restoration of at least 15% of degraded ecosystems. This target has, however, not been fulfilled so far. In 2018, the "Environmental Policy Strategy" defined goals for 2030 stating that "ES are evaluated and quantified and they will be considered for investments and policy-making, as well as for environmental impact assessment". Nevertheless, Slovakia currently has one of the lowest ES implementation rates in Europe. The MAES assessment records only 20% implementation for the Slovak Republic, which puts it at the lowest ranking together with Cyprus (BISE 2019).  provided an assessment of the current state of ES implementation in Slovakia for planning and decision-making processes;  also explicitly address ES integration in both of these spheres. Although these studies provided the basis for better implementation of the ES concept in our country, recent ES research is still scattered over various institutions, resulting in partial case studies that lack unity. Mederly and Černecký (2019) provided an overview of the "state of the art" of the ES research in Slovakia and find that the main ES implementation challenge has not yet been met.
To address the issues mentioned above, the main aim of this research is to prepare and present a pilot national ES assessment for the Slovak Republic. This goal partly addresses the policy targets of both of the above-mentioned national framework documents. Our research also supports the Ministry of Environment's MAES expert working group mission, which focuses on Target 2 of the EU Biodiversity Strategy. Furthermore, the scientific goal of our research is to establish a comprehensive biophysical approach for national ES assessment based on a development of unique computational procedures of ES assessment, drawing on a complex database of natural and partly socio-economic features.

Material and methods
Our research covers the entire 49,034 km² territory of the Slovak Republic, which is a landlocked country in Central Europe. The December 2019 national census identified 5,457,873 inhabitants in a dense settlement network administered by 2,890 municipalities. These include 140 cities with 53.5% of the population; there are only two cities with over 100,000 inhabitants and 10 more with over 50,000 (STATdat 2020). Most Slovak territory and, especially, the northern and central mountain areas, are in the Carpathians biogeographical region. The remaining areas, mostly in the south, lie in the Pannonian lowland plain. Agricultural land covers 40.1% of the territory, forest covers 40.2% and 19.7% belongs to other land-use classes, including settlements.
For the ES assessment, we followed a straightforward path: specifying which ES were to be addressed of ES addressed, gathering data and setting the assessment process and finally proceeding to the computation, standardisation and interpretation of the results. Fig. 1 provides the scheme of the research procedure.

Ecosystem services selection
The assessment process employs the standard ES classification with three main groups, from which 18 ES were selected -five provisioning, 10 regulatory/maintenance and three cultural ES. This selection resulted from expert determination of significant Slovak ES in the MAES process -in total, more than 20 experts from 14 governmental and scientific institutions (Ministries and their research institutions, universities and other academic institutes) were involved in this process. In addition, existing national assessment studies and review research (Schröter et al. 2016, Nedkov et al. 2018) influenced our selection.  The scheme of the research procedure.

Data preparation and standardisation
For the assessment of individual ES, we mainly used data from available spatial and information datasets. We initially prepared all spatial layers and database information in a unified form, relying primarily on the internal datasets of organisations involved in this research. We also added available data from environmental agencies and specialised institutions and open data from Slovak and European cartographic and remote sensing resources. Table 2 provides the list of map layers (41 in total) used for the initial assessment process. Some of them we prepared as tailored layers by reclassification or computational algorithms from raw data and then they were used as intermediate assessment layers.  Table 2.

Content (theme) of the map layer
List of map layers used for assessment of ecosystem services in Slovakia.

Content (theme) of the map layer
Source of data Data scale Prod. Reg. Cult. The essential layers, used in the assessment of most ES, include the following: a map of current land use/landscape structure and its interpretation; a map of ecosystems and selected derived features (Černecký et al. 2019); specific forest datasets; data on protected areas, a digital elevation model and soil properties. The detail and accuracy of the data are set in 1:25,000 scale, which is well above the national assessment standard. Supplementary input information includes selected climate and hydrological data at the 1:50,000 national accuracy level. For the cultural ES, we also used less accurate data from the Slovak Landscape Atlas (MoE SR 2002).

Significant watercourses
Our next step was to standardise the data. We converted all used layers from different sources to the same shape -a raster format with a pixel size of 25 m, in the S-JTSK coordinate system. During the assessment process, we kept all calculations in this format. Table 2 supplies the list of employed data, information sources, accuracy and importance for ES assessment. A full description of data is provided in Suppl. material 1.

Setting up the computation models
To express the landscape's relative capacity to provide all valued ES, we employed a coordinated procedure, based mainly on spatially-expressed biophysical and environmental data (see previous point).
For this purpose, we used a qualitative expression of the landscape capacity for ES provision on a dimensionless relative scale (0 to n points). A computational algorithm was developed for each ES in consultation with team members with expertise in that ES, based on the different input layers. Computational procedures consisted of the reclassification and overlay of different data layers. The approach used could be considered one of the main innovations of our research. The essential landscape properties entering the computation of given ES are provided in Table 1; Table 2 gives a full overview of the data. For the data used and the computational algorithms for all ES, see Suppl. material 2.
By using this procedure, we produced 18 detailed ES landscape capacity maps on a 25 x 25 m grid, with different numeric values (generally from 0 to n points). The rough ES maps then went through a process of results standardisation (see next subsection). The final ES values use a relative 0-100 scale, where 0 indicates the minimum current capacity of any area in Slovakia for the provision of the given ES and a value of 100 represents maximum current capacity. Since the distribution of the majority of the ES capacity values was highly asymmetric and did not meet the preconditions for a statistically normal distribution, before the final transformation of the maps into the 0-100 scale, we proceeded to remove data outliers (those within 2% of the minimum and maximum values).

ES results standardisation & visualisation
The final values, in a dimensionless scale, can be interpreted as a suitability scale from minimum (0%) to maximum (100%) landscape capacity for providing ES. Additionally, classification into several degrees of suitability is possible, for example, below average, average, above average and high to very high capacity, based on the percentile distribution of values.
The resulting ES maps for the territory of Slovakia contain about 49 000 pixels with individual values for each ES. They represent a basic statistical set suitable for further assessment of the interactions and factors affecting the provision of the ES.
For the graphical presentation of the ES maps, we chose a unified form: maps show the relative capacity of a landscape to provide a given ES in a 5-degree legend (every 20% of the scale is represented by one shade of a colour scale). Suppl. material 3 shows the histograms, box plots and maps of all 18 ES. Detailed results of the assessment of 18 individual ES for Slovakia, including the theoretical and methodological background, were published by Mederly and Černecký (2019).

Assessment of the ES groups & overall ES assessment
The main goal of our research is to introduce and assess those ES significant for the territory of Slovakia. Of course, staying only at the individual ES level without the assessment of ES groups and the overall ES would be insufficient. For this reason, we also decided to carry out assessments of the three main ES groups and a map of the landscape's overall capacity for ES provision.
For the computation of the landscape capacity for provisioning, regulatory/maintenance and cultural ES, we used a simple arithmetic average of the value of all ES in a given group (five ES, 10 ES and three ES). Evaluating the landscape's overall capacity to provide the ES required us to determine the weight (importance) of three main ES groups.
Due to varying opinions about the importance of the ES groups in the research community, we decided to handle this problem in a relatively simple, but (in our opinion) sufficiently representative and "fair" way. In our approach, provisioning ES as a whole is weighted at 25% of the total weight, the same weight being applied for cultural ES. Regulatory/ maintenance ES constitute 50% of the total value. Finally, we calculated the resulting value as the sum of the capacity values for each ES group multiplied by the given weight. The theoretical value of the capacity ranges (as in the case of individual ES) from 0 to 100, where 0 means no capacity and 100 the maximum possible landscape capacity for ES provision.
An overview of the results for all ES groups is provided in the result section.

Results interpretation & discussion
Our ES assessment aims to cover the territory of Slovakia and, thus, is fundamentally orientated towards giving a national overview. In addition to this objective, we also tried to explain two ES spatial distribution factors: (1) the relationships between the main landscapes types and ES provision and (2) the importance of land use classes for ES provision. We used basic methods of spatial statistics for this interpretation; the last results subsection briefly summarises the findings.
In the discussion section, we seek to compare our approach to other national assessment studies and try to highlight some advantages and disadvantages of our methodology and discuss challenges for future research.

Results
In this section, we provide an overview of the results obtained for the three main analysed ES groups and overall ES assessment, together with interpretation of the results. Tables, charts and maps are used to illustrate the results.

Provisioning ES
Provisioning ES are perceived and directly appreciated by most people. These include physical products and goods from ecosystems which provide the following: nutrition, materials and energy, biomass for food, drinking water and water for other purposes, useful biomass, abiotic materials and substances and energy resources (MEA 2005 and others). Herein, we selected five ES for our pilot assessment based on the opinion of the MAES process experts from various Slovak institutions.
For the five assessed provisioning ES, the mean capacity values range from 13.2 (P3) to 34.5 (P5) -see Fig. 2. Basic statistic parameters are presented in Table 3, while Suppl. material 3 provides individual ES maps. 1. ES Biomass -Agricultural crops and fodder is one of the "most visible" ES in the agricultural production process. The problem with biomass-agricultural crops is that the use of most other ES is largely suppressed or even eliminated by the intensive use of this ES. The spatial distribution of landscape capacity to provide this ES is significantly different from most other provisioning ES because, while the highest landscape capacity values are typically found for lowland areas with fertile soils and mild climate, the lowest values are found in high mountain areas. 2.
ES Biomass -Timber and fibre. Although this is mainly provided by forestry, agriecosystems and other landscape types are also involved in this ES provision. Wood biomass and the benefits it provides, tends to grow on a decades-long timescale and a one-time benefit from this ES can cause decades of "loss of benefit" in the areas of other ES. This factor is largely neglected by sectoral landscape management. From spatial projections of this ES in Slovakia, we find Table 3.
Basic statistical parameters of the provisioning ES*1.

Figure 2.
Histogram and plot of the provisioning ES values*1.
that the highest landscape capacity values are found for lower mountain areas and transitional sub-mountainous landscapes. 3.
ES Drinking water and 4.
ES Freshwater are closely related and sometimes considered and assessed as one ES. The landscape capacity for these ES mainly depends on abiotic conditions and processes, such as rainfall-runoff balance and hydrogeology. However, ecosystem status and environmental quality are also important, especially for drinking water which is concentrated in larger accumulations of water. The freshwater potential in mountain ranges is high with natural accumulation capacity and the wider river valleys and floodplains with quaternary gravel accumulation are of particular importance. 5.
ES Fish and Game/Wild-food depends to a great extent on the predominant land use types, environmental quality and the regulations on fish and animal capture.
Although wild-food dominates in lower and medium-altitude mountain ranges, the lowlands and basin areas also have great potential, especially in sub-mountainous areas and close to large bodies of water. This ES little with other ES because it does not fundamentally affect other ES benefits. Fig. 3 shows the spatial projection of the overall capacity of the Slovak landscape to provide provisioning ES expressed as the average of the five evaluated ES. Small discontinuous areas in the Slovak higher and middle-elevation mountain ranges and forest areas achieve the highest ES levels and some lowlands and basin areas also have high levels. The landscape's lowest capacity to provide provisioning ES is found in urbanised and densely-populated areas and the less productive and non-forested parts of the lowlands and higher river basins. In addition, the highest parts of the mountain ranges also have limited capacity for provisioning ES. The overall capacity of the landscape to provide provisioning ES.
National ecosystem services assessment in Slovakia -meeting old liabilities a ...

Regulatory & Maintenance ES
Regulation ecosystem functions and services should be considered critical, because many natural processes have a positive influence on the environment and all living species' health and well-being. For the assessed regulatory/maintenance ES (Fig. 4), the mean capacity values range from 5.6 (R3) to 49.7 (R4). Basic statistic parameters are presented in Table 4, while Suppl. material 3 provides individual ES maps.  1. ES Air quality regulation mitigates the effects of air pollution on ecosystems and. therefore. also on humans. Forest ecosystems cover over a third of the Slovak land-mass and, from a national viewpoint, these are clearly the most important in the provision of the regulation of air quality ES. Other ecosystems, such as built-up Table 4.
Basic statistical parameters of the regulatory/maintenance ES*2. areas, can have local significance, because these areas impose the highest demand on and consumption of air quality ES.

ES Water quality regulation: this ES depends on different biophysical parameters.
It is primarily provided by Slovak Medio-European beech forests and other wooded ecosystems, because of their quantity and favourable conservation status. Besides these ecosystems, mires, bogs and fens have a significant influence on provision ES Water quality regulation, but these habitats cover only 0.43% of Slovak territory. 3.
ES Erosion and natural hazard regulation depends on the ability of the ecosystem and landscape to regulate adverse relief processes and to prevent and mitigate erosion, landslides and other gravitational processes. We chose water erosion regulation for the pilot assessment. While permanent grasslands provide very high anti-erosion effects, the main landscape type that provides this ES is the forested areas of hills, highlands and mountainous areas with appropriate spatial structure and quality. 4.
ES Water flow regulation expresses the river catchments ability to regulate water runoff during extreme rainfall events so that flooding is avoided and risks are minimised. Natural and well-functioning watercourses, wetlands and valley ecosystems are best able to transform flood waves and high-water levels into lower basin areas -this is the principal mechanism of ES Water flow regulation. The open broad river valleys, water reservoirs and lowland landscapes with sufficient forests or water elements have the highest capacity for providing this ES out of all the Slovak landscape. 5.
ES Local climate regulation affects the ability of ecosystems to regulate temperature, the amount of incident solar radiation and the spatial distribution of micro-climate factors (precipitation, wind, evapotranspiration). Mitigating the effects of pollutants, dust and noise-related processes also belongs to the crucial functions. Forests and woodlands are the main Slovak ecosystem types which provide this ES. This ES is also provided in lower quantity but high quality by water bodies, watercourses and riparian vegetation. 6.
ES Global climate regulation is in our assessment represented by carbon sequestration. It consists of biogeochemical and biophysical processes which help avoid the adverse effects of global warming on humankind and biodiversity. Forest ecosystems participation in this ES is most prominent. The most widespread habitats which provide this ES in Slovakia are the beech forests and lowland hay meadows. The most qualitatively significant carbon pools are peat bogs. 7.
ES Biodiversity promotion. Mountain and submountainous areas, together with grasslands, have the highest capacity to provide this ES because a significant proportion of their natural and semi-natural habitats are a part of the network of protected areas. The higher biodiversity there promotes ecosystem functioning, contributes to the maintenance of ecological stability and increases the terrestrial and freshwater ecosystems' potential to provide societal benefits. 8.
ES Pollination is an essential ES because insect pollination has a significant and irreplaceable impact on ecosystem dynamics and thus supports multiple provisioning services. Forests and wooded habitats provide the high quality of this ES, especially beech, fir-beech, lime-oak and oak-hornbeam forest systems.
Pollination is also an essential ES in the orchards and submountainous haymeadow and flowering-meadow habitats. 9.
ES Pest and disease control. Healthy ecosystems with favourable conservation status can mitigate or resist the spread of disease and invasive non-native species through genetic variation. Our research highlights that natural and semi-natural diversified habitats around agro-ecosystems and urban areas provide the highest capacity for this ES. Moreover, the demand for ES in these areas is obviously quite high. 10.
ES Soil formation. Soil properties are essential for both functioning of the agricultural landscape and other types of ecosystems which provide different nature functions. We find that, in addition to high quality agricultural soils, this ES is provided at a high level by natural and semi-natural forest and grassland ecosystems. Furthermore, watercourses, water bodies and wetlands play a significant role as transformation media for nutrient transfer to soils. Fig. 5 illustrates the overall capacity of the Slovak landscape for regulatory/maintenance ES provision and shows that the highest value is present in forested mountain and foothill areas. Other mountain ranges and sub-mountainous areas provide medium to relatively high landscape capacity, while lowlands and basin areas with predominantly arable land have a low ES capacity.

Cultural ES
Most cultural ES are challenging to measure, monitor and model and other authors assert that the value assigned to natural and cultural heritage often depends on individual and cultural assessment of their contribution to human well-being (Charles and Dukes 2008). Beauty, aesthetics and visual quality are perceived individually, with each person preferring The overall capacity of the landscape to provide regulatory/maintenance ES. a different type of landscape. Moreover, although cultural ES are tied to given landscape types, it is evident that all landscapes have something to offer in the way of natural assets and cultural and historical monuments.
We have, therefore, used the most recent available biophysical methods in assessing the landscape capacity for cultural ES provision based on available datasets. For the assessed cultural ES (Fig. 6), the mean capacity values range from 17.1 (C3) to 27.5 (C2). Basic statistic parameters are presented in Table 5 1.
ES Recreation and tourism. The most obvious and apparent cultural ES. We evaluated it using available data on current landscape structure and the use and location of significant monuments and natural, historical and cultural sites of Table 5.
Basic statistical parameters of the cultural ES*3. interest. Information on protected areas and relevant data on tourist areas and routes and sport and leisure facilities also supplemented our assessment. 2.
ES Landscape aesthetics. This ES express the visual quality of the landscape. We make our assessment on a reclassification of the aesthetics and attraction of land use classes, the occurrence of unique landscape structures under traditional land use and the attraction of the surrounding relief. 3.
ES Natural and cultural heritage. This ES considers the importance of valuable natural and cultural sites for human existence. Here, we gave the special consideration to UNESCO sites, other historical and cultural monuments, protected areas and historical landscape structures under traditional management.
We expressed the landscape's overall capacity for cultural ES provision as the average of the three assessed ES (Fig. 7). They are closely related and have similar spatial distributions. The figure shows that the highest value is found for the high Carpathians and, especially, for the Tatra mountains. High values are also found for the mountain areas containing biosphere reserves and UNESCO sites, while most other Slovak mountain and sub-mountainous areas have medium-to high-capacity ES levels. Most of the lowlands and the central parts of the intra-mountain basins have low capacity values.

Overall ES assessment
As a synthesis of the first stage of our national ES assessment, we compiled the landscape's overall capacity for ES provision and calculated this value as the weighted average of values for the three assessed provisioning, regulatory/maintenance and cultural ES groups (see section Material and methods). Table 6 provides basic statistical parameters and Fig. 8 a histogram of these values. The overall capacity of the landscape to provide cultural ES.  Fig. 9 gives the spatial distribution of the overall landscape capacity and highlights the fact that the most essential areas of Slovakia for overall ES provision capacity are the large areas of lower and medium-high mountains (which mostly have a capacity value of 50-60).
In contrast, the areas at the lower end of the ES capacity scale are generally the broad Slovak lowlands and open basin areas (capacity value 15-25). Table 6.
Basic statistical parameters of the analysed ES groups*4.

Figure 8.
Histogram of the overall ES values.

Result interpretation
Ecosystem functions and related services are substantially based on the natural structure of the landscape and it is, therefore, useful to assess the main spatial units' capacity for ES provision. These basic Slovak landscape types are classified as the combination of the main Pannonian and Carpathians biogeographical regions and the geomorphological landscape types found in the area, which include the lowlands, river basins, the low and sub-mountainous regions and the mid-altitude and high mountain areas.  Figure 9.
The overall capacity of the landscape to provide ecosystem services. 1. the ES capacity is significantly higher for the mountain areas than for the lowland and basin areas; 2.
the capacity of the "core" Carpathians high altitude mountains is the highest for all ES groups; 3.
the middle-and low altitude mountains have high significance because the former are essential for cultural and regulatory/maintenance ES and the latter have greater importance for provisioning ES and 4. river basin areas have higher ES capacity than lowlands, with the exception of provisioning ES.  The overall capacity of the landscape units to provide ecosystem services. Fig. 11 shows the relationship between land use/land cover types and their overall capacity to provide ES. Here, the land use has been directly entered into the computational algorithms for most ES, so this assessment provides only a summary of the contribution of individual landscape categories to ES provision. The statistical results confirm the consensus that forests are the most essential ecosystems for ES provision and urbanised areas are the least important.
The highest landscape capacity value for ES provision (1.5 times the average Slovak value) is found for deciduous forests, followed by mixed and coniferous forests. Rocks and screes have a very high capacity for cultural ES provision, while water bodies and wetlands have a high capacity for all ES groups. In contrast, permanent grasslands, orchards and vineyards have an average capacity for ES provision and arable land and urbanised areas have low to very low capacity.
Brink ten (2013) and other authors claim that NATURA 2000 protected areas have a crucial influence on the European Union's natural capital. We have, therefore, also focused on assessing the relationship between nature protection and the landscape's capacity for providing ES. The results show a clear correlation between these two indices for most ES. This fact is particularly evident for cultural ES and most regulatory and maintenance ES . The highest capacity for providing these ES comes from natural and semi-natural ecosystems which are often involved in nature protection area systems. We found the most pronounced positive correlations for the following ES: Air quality regulation, Erosion and natural hazard regulation, Biodiversity promotion and Pest and disease control and we noted a clear positive correlation for all three assessed cultural Figure 11.
The overall capacity of the landscape to provide ES for the main categories of land use*4.
ES. These results emphasise the critical importance of nature and landscape protection for a healthy ecosystem state and the fulfilment of their functions and provision of services directly and indirectly used by humans.

Discussion
ES mapping and assessment has developed into a very mature scientific field in recent years (Burkhard and Maes 2017). ES maps are a powerful tool for communicating land use trade-offs and for transforming biodiversity, ecosystem and ES data into policy-and decision-making. However, comprehensive ES assessment must distinguish three essential aspects (Burkhard et al. 2014). These are, firstly, the landscape's capacity (supply) for ES provision; secondly, ES demands in a particular territory; and thirdly, ES actual use and balance as ES flow.
Analysis of national ES assessments (NEAs) finds that full implementation of ES in decision-making is still uncommon and Schröter et al. (2016) stress that the NEAs are highly context-specific for national policies and stakeholder interests and also for environmental settings and socio-economic characteristics. The design of the ES framework must, therefore, include country-specific adaptations.
Several countries have made significant progress in NEA research using a wide variety of approaches. Dimopoulos et al. (2017) The assessment is generally composed of two basic steps: the first involves mapping the ecosystem types and assessing ecosystem conditions and the second involves detailed ES mapping (e.g. Dimopoulos et al. (2017) in Greek ES assessment). Some approaches use GIS-based data and reclassification methods, for example, Denmark's spatial analysis of 11 ecosystem services in a 10 ×10 km grid ). Assessment of ES capacity for Lithuania (Depellegrin et al. 2016) uses 31 CLC classes and 31 ES categorised into three main ES groups. Their expert-based ranking approach using a two-dimensional ES matrix and a geospatial analysis was then applied to determine the total ES potential and spatial patterns and the relationships between multiple ES. The Lotan et al. (2018) Israeli study considered potential pollination and genetic resources and the recreational use of the evaluated ES and Arany et al. (2018) conducted an integrated ES assessment in Hungary using the cascade model levels of ecosystem mapping to identify ES capacity and its use and contribution to human wellbeing. The NEA for the Czech Republic made an innovation in ES national monetary assessment of employing the "benefit transfer" method of converting the specified worldwide economic values for individual ES to national conditions (Frélichová et al. 2014 The capacity to provide regulatory/maintenance ES depends mainly on the quality of a given ecosystem and its associated land use. In Slovakia, the frequent occurrence of windand bark-calamities and subsequent large-scale harvesting in the last 10-15 years have had negative impacts on the stability of forest ecosystems and this is undermining provision of the forest regulatory ES. Investigation of forests in Slovakia, affected by natural disturbances and changes in climate and land-use (e.g. Fleischer et al. 2017), shows declines mainly in cultural and provisioning services. Thom and Seidl 2015 analysed the impact of the most important disturbance agents and the effect on different ES and biodiversity of commonly used management approaches. They found that the disturbance impacts on ES are generally negative and the management approaches considered (e.g. salvage logging) do not mitigate adverse effects on ES nor enhance positive effects on biodiversity.
The importance of the agricultural and urban landscape in the provision of cultural ES has increased in recent years. This is mainly due to the development of agri-tourism and the current emphasis on healthy lifestyles which makes use of, for example, urban parks and vegetation for leisure activities (Santos-Martín et al. 2016). On the other hand, the use of cultural ES is limited by the effects of stress factors including environmental contamination from radiation, polluted air and water, damaged forest ecosystems and noise (Santarém et al. 2020) -all of which are related to the demand for regulatory and maintenance services.
Our results also confirm the importance of mountains for ES delivery, as has been found by other NEA (e.g. Skre 2017,Crouzat et al. 2019. Some authors find differences between mountain areas where demand and supply are well balanced and areas where demand and supply are unbalanced (Grêt-Regamey et al. 2012). It must also be taken into account that the spatial flows of ES from and to mountain regions extend far beyond the regional level (Schirpke et al. 2019 ES provision in addition to the recognised ecosystems types and land use. One of its greatest strengths is the use of a comprehensive approach for 18 ES, with a single methodological framework, a shared database and use of the same spatial scalefeatures which enable detailed comparison of individual ES. Nevertheless, in the case of cultural ES, additional work is necessary to ensure more appropriate overall ES assessment by incorporating later or more accurate data from state statistical surveys; especially at the municipality level. We consider the expression of the landscape's overall capacity for ES provision a particular problem. Most studies at a national or regional scale remain at the level of individual ES or their groups. Within this context, they evaluate synergies and trade-offs and rarely consider the overall capacity of the main ES groups (e.g. Jäppinen and Heliölä 2015). We have not found another national study presenting an overall ES assessment on a relative scale (suitability scale, %). Nevertheless, the situation is different in the case of monetary ES valuation, where the calculated financial values could simply be summarised -which is, incidentally, the case for estimating the ES global value (e.g. Costanza et al. 2014) and the national-level case of the Czech study (Frélichová et al. 2014). Looking for an appropriate synthesis of ES capacity biophysical values and linking it with economic valuation is undoubtedly one of the main challenges for our further research.
It is clear, that our approach is "science-driven" and not "policy-driven" because the views and attitudes of different stakeholders are not considered. This is a shortcoming compared to certain other national studies (e.g. Spain, Finland, Norway, Flanders and the United Kingdom) which, according to the review by Schröter et al. 2016, have incorporated stakeholder participation, collaboration and cross-sector communication into the assessment process. The next step, therefore, should be an integration of our results with policy-relevant questions and policy-impact assessments. It should also include assessment of other aspects of ES provision, including their current flow in the landscape, the demand for individual ES and monetary assessment of the benefits that ecosystems provide, as stressed by, for example, Braat and de Groot (2012).
Spatial ES flows and their inter-relationships in different scales also offer an interesting direction for future research. These topics cover ES flows from the mountains to the lowlands (Schirpke et al. 2019) and also in trans-boundary and conflicting regions (Santarém et al. 2020) which include urban and rural areas (Haberman and Bennett 2019). The increasing evidence of the natural environment's positive impact on mental health also mandates the need for such an assessment (Bratman et al. 2019). Here, quantification of the effects of land use and climate change on ES is possible through scenarios and modelling of both current and future potential ES status (Krkoška Lorencová et al. 2017). These are, also, further challenges for our ongoing research.

Conclusions
The main aim of our research was to conduct a pilot assessment of those ES, which are most relevant for the territory of Slovakia. While other national studies have inspired our research, we have herein introduced an original methodology, based on an individual computational algorithm for assessment of the ES using a database of 41 natural and societal landscape parameters. Evaluation of the 18 individual ES is followed by assessment of provisioning, regulatory/maintenance and cultural ES.
The highest capacity to provide ES comes from natural and semi-natural ecosystems, especially the deciduous, coniferous and mixed forests which cover more than 38% of Slovak territory. Other ecosystems, particularly those in the Carpathians, proved very valuable for the provision of many different ES. Moreover, this paper highlights the crucial importance of the high mountain areas of Slovakia for ES provision.
The results of the Slovak national ES assessment have been published as a comprehensive scientific publication (Mederly and Černecký 2019). The intent is for these results to be distributed and used in the field of nature protection, management of natural resources, spatial planning at different spatial levels and, last but not least, as a textbook for university studies of environmental sciences. We now intend further research which will more precisely examine selected socio-economic parameters which affect demand for most ES. In addition to population, human activities and resource use, our research will focus on the quality of the environment as a primary indicator for regulatory/maintenance ES. Further work will then centre on the current ES flow in the landscape and economic and financial ES assessment at the national level, followed by evaluation of spatial and functional mismatches and trade-offs of the ES over the entire territory of Slovakia.