Sustainable Development of Rural Areas in Poland since 2004 in the Light of Sustainability Indicators

: Sustainable development of a region requires sustainability of its rural parts, as a source of supplies and resources for the urbanized regions. The current climate changes, loss of biodiversity, limited resources, depopulation, deterioration of economic conditions or even poverty may limit the sustainable development of rural populations. This paper presents the study concerning assessment of sustainable development of rural areas in Poland since 2004, the date of Poland entrance to the European Union, in light of the selected Sustainable Development Indicators. The assessment was based on the set of 38 indicators covering environmental, social and economic pillars of sustainability. The results of this study indicate the signiﬁcant progress in some aspects of rural development in Poland since 2004. However, several serious limits for rural sustainability were identiﬁed, including limited access to basic services including sanitation, anthropopressure on the natural environment, limited access to clear and renewable energy, depopulation, ageing, unfavorable economic conditions and relatively low productivity of agriculture.


Introduction
The concept of sustainable development as used today was presented in 1987 by the World Commission on Environment and Development (WCED) [1] in their report, Our Common Future. It was also introduced in 1997 to Article No. 5 of the Constitution of the Republic of Poland [2]. According to the cited report, sustainable development was defined as a process aimed at satisfying the development aspirations of the present generation while preserving the possibility of satisfying the same aspirations by future generations. At the same time, it was strongly emphasized that sustainable development is a process in which there should be simultaneous integration and harmonization of activities in the economic, social and environmental spheres on a global scale [3,4]. The developed complicated and complex strategies of sustainable development, realized with respect to nature and the rule of intergenerational justice, should integrate all the above-mentioned circles of sustainability [5,6].
Within the Sustainable Development Strategy of the European Union [7], established in 2001 and modified in 2006, four main objectives of actions were defined, which included protection of the natural environment, justice and social cohesion, economic prosperity and implementation of the EU commitments on an international stage. The basic challenges of the strategy were climate change and clean energy, sustainable transport, consumption and production, protection and management of natural resources, public health, social integration, demography and migration, challenges in the field of global poverty and sustainable development.
The increasing popularity of sustainable development, as well as formulation and enactment of strategies of sustainable development, resulted in the necessity of quantified  The rural areas in Poland are divided into 1523 rural and 652 rural-urban communities governed by the local governments, selected in anonymous, universal, direct and equal elections [66,68]. According to abiding law in Poland, the local governments are responsible for assuring meeting the common requirements of self-governmental communities [69], including issues related to environmental, social and economic sustainability.

Method of the Study
The assessment of sustainable development of rural regions of Poland since 2004, the date of Poland's entry to the European Union, was based on the set of useful, measurable and easily accessible Sustainable Development Indicators (SDIs) presented in Table 1. The total number of 38 indicators, from three main circles of sustainability, i.e., en- covered approx. 90.1% of country area (the total area of Poland is equal 30,610,010 ha), including 59.9% share of arable lands and 30.2% of forests. The actual land usage in Poland is presented in Figure 1. According to the General Agricultural Register [67] performed in 2020, the number of agricultural farms in Poland was approx. 1,317,000 with the mean area of arable soils 11.1 hectares. The registered number of farms decreased since 2010 from approx. 1,509,000 but the average area of a single farm increased (from 9.8 ha). However, still more than 50% of farms in Poland have an area smaller than 5 hectares. The total registered population of Poland at the end of 2021 was 37,907,704, of which 15,283,690 were the residents of rural areas, consisting of 40.32% of Poland's population, see Figure 2.  The rural areas in Poland are divided into 1523 rural and 652 rural-urban communities governed by the local governments, selected in anonymous, universal, direct and equal elections [66,68]. According to abiding law in Poland, the local governments are responsible for assuring meeting the common requirements of self-governmental communities [69], including issues related to environmental, social and economic sustainability.

Method of the Study
The assessment of sustainable development of rural regions of Poland since 2004, the date of Poland's entry to the European Union, was based on the set of useful, measurable and easily accessible Sustainable Development Indicators (SDIs) presented in Table 1. The total number of 38 indicators, from three main circles of sustainability, i.e., en- The rural areas in Poland are divided into 1523 rural and 652 rural-urban communities governed by the local governments, selected in anonymous, universal, direct and equal elections [66,68]. According to abiding law in Poland, the local governments are responsible for assuring meeting the common requirements of self-governmental communities [69], including issues related to environmental, social and economic sustainability.

Method of the Study
The assessment of sustainable development of rural regions of Poland since 2004, the date of Poland's entry to the European Union, was based on the set of useful, measurable and easily accessible Sustainable Development Indicators (SDIs) presented in Table 1. The total number of 38 indicators, from three main circles of sustainability, i.e., environmental (16 indicators), social (10 indicators) and economic (12 indicators), was used. The assumed percentage, i.e., 42%, 26% and 32%, share of selected SDIs for each criterion corresponds to values reported by [34,35]. The indicator selection was influenced mostly by the official data availability for rural areas and for the period 2004-2021 under consideration; only several included SDIs with shorter data range were used in the study. The assumed set of indicators reflects also the commonly accepted selections to such analyses performed in the past for Poland, including its rural parts, and for the other regions [42,53,63,64]. However, the applied number of indicators in this study is greater than in the previously published studies [42,53,63,64]. Additionally, the proposed SDIs set is in agreement with the indicator selection suggested by the EU policy [70,71]. The values of indicators used in this study were obtained from the official Polish governmental database of the Central Office of Statistics [67] and the European Union database Eurostat [70]. The presented analysis was based on time-related changes in reported SDIs values for the assumed duration 2004-2021, as well as determined descriptive statistics, including minimal, maximal and mean values, calculated percentage increase/decrease in indicator value. The percentage increase in SDI was determined as follow: where: ∆SDI % -percentage change of SDI value for given period, SDI i -indicator value for the initial year of assessment, SDI f -indicator value for the final year of assessment. The groundwater quality in rural regions was assessed basing on the available results of the annual operational groundwater monitoring for selected sampling points in rural areas (rural settlements, arable lands, meadows, vegetation and forests) provided by The Polish Geological Institute National Research Institute [72] for period 2004-2021. The water quality was qualified according to the abiding Polish law [73,74] as five classes: I-very good quality, II-good quality, III-satisfactory quality, IV-unsatisfactory quality and V-bad quality, respectively. The groundwater quality class is determined according to threshold values of 55 water quality indicators [61,62].

Environmental Sustainability
In our opinion, availability of freshwater resources endangered by anthropopressure related to sanitary sewage management and treatment is a crucial aspect of environmental sustainability. Figure 3 presents time-related groundwater quality in rural regions of Poland for the period 2004-2021 determined according to the legal water quality classes [73,74]. The presented annual monitoring results were obtained for variable monitoring points, in range 242-1067, located in rural regions of the country.
(% of total emission) Greenhouse gas emissions from agriculture (% of total emission) Estimated soil loss by water erosion (tone/hectare) Area of organic farming (%)

Environmental Sustainability
In our opinion, availability of freshwater resources endangered by anthropopressure related to sanitary sewage management and treatment is a crucial aspect of environmental sustainability. Figure 3 presents time-related groundwater quality in rural regions of Poland for the period 2004-2021 determined according to the legal water quality classes [73,74]. The presented annual monitoring results were obtained for variable monitoring points, in range 242-1067, located in rural regions of the country.  [73,74], data obtained from [75].
As is visible in Figure 3, the class I of groundwater quality was determined only for limited number of observation points, up to 8.6%. However, the dominant classes are III and II, i.e., satisfactory and good quality. On the other hand, the significant share of unacceptable groundwater quality may be noted during the discussed time duration. The sum of unsatisfactory and bad quality reports covers 17.9-30.0% of all the rural monitoring stations.
According to Eurostat data for 2016, presented in Figure 4, the agricultural land in Poland is endangered by estimated soil erosion below the EU mean value, i.e., 1.5 tons per hectare in Poland versus 3.4 tons per hectare for the EU. Thus, the possible soil loss due to intensive soil erosion should not significantly limit the agricultural activities in the rural areas of Poland.  [73,74], data obtained from [75].
As is visible in Figure 3, the class I of groundwater quality was determined only for limited number of observation points, up to 8.6%. However, the dominant classes are III and II, i.e., satisfactory and good quality. On the other hand, the significant share of unacceptable groundwater quality may be noted during the discussed time duration. The sum of unsatisfactory and bad quality reports covers 17.9-30.0% of all the rural monitoring stations.
According to Eurostat data for 2016, presented in Figure 4, the agricultural land in Poland is endangered by estimated soil erosion below the EU mean value, i.e., 1.5 tons per hectare in Poland versus 3.4 tons per hectare for the EU. Thus, the possible soil loss due to intensive soil erosion should not significantly limit the agricultural activities in the rural areas of Poland.  The environmental quality in rural regions, directly affecting the quality of life of the rural population is, in our opinion, highly related to the development level of water and sewage services available for the residents. Figure 5 presents percentage share of the rural population in Poland connected to organized water, sanitary sewage and gas, as well as the difference (in % of population) between residents connected to water and sewage networks in rural and urban areas. The environmental quality in rural regions, directly affecting the quality of life of the rural population is, in our opinion, highly related to the development level of water and sewage services available for the residents. Figure 5 presents percentage share of the rural population in Poland connected to organized water, sanitary sewage and gas, as well as the difference (in % of population) between residents connected to water and sewage networks in rural and urban areas. The environmental quality in rural regions, directly affecting the quality of life of the rural population is, in our opinion, highly related to the development level of water and sewage services available for the residents. Figure 5 presents percentage share of the rural population in Poland connected to organized water, sanitary sewage and gas, as well as the difference (in % of population) between residents connected to water and sewage networks in rural and urban areas. Figure 5. Accessibility of rural water, sewage and gas supply networks in Poland, data obtained from [66]: (a) rural and urban population connected to organized water, sewage and gas networks, (b) difference between population connected to water and sewage networks.
It is visible in Figure 5 that the tap water supply development in rural areas is satisfactory; in 2021, 85.9% of the rural population were connected to the organized water supply networks (the value for the urban population reaches 96.7%, see also Table 2). In 2004, these values were 71.3% and 94.4% for rural and urban residents, respectively. On the other hand, we may state that development of organized rural sanitary sewage system is unsatisfactory. In 2021, only 43.8% of the rural population in Poland had access to sewage systems. However, in 2004, this number was more than two times lower, i.e., 17.3% of rural residents. In comparison, the access to sewage by the urban population It is visible in Figure 5 that the tap water supply development in rural areas is satisfactory; in 2021, 85.9% of the rural population were connected to the organized water supply networks (the value for the urban population reaches 96.7%, see also Table 2). In 2004, these values were 71.3% and 94.4% for rural and urban residents, respectively. On the other hand, we may state that development of organized rural sanitary sewage system is unsatisfactory. In 2021, only 43.8% of the rural population in Poland had access to sewage systems. However, in 2004, this number was more than two times lower, i.e., 17.3% of rural residents. In comparison, the access to sewage by the urban population varied between 84.0% and 90.7% of residents. A similar situation may be noted for organized gas supply networks; currently, only 28.8% of the rural population (in comparison to 72.3% of urban residents) has access to clean fuel, allowing to reduce the significant anthropopressure on the natural environment exerted by the fossil fuels used for heating.   Figure 6 shows the time-related lengths of rural water and sewage networks and annual investments in these systems' development. It is visible that the state and local authorities were aware of the unsatisfactory development of rural sanitation and, in combination with the outside financial support of the EU, significant investments in sewage systems were provided, especially after 2009. The presented investments and increased length of rural water supply systems may be correlated to the visible increase in water consumption by rural residents, from 22.6 m 3 to 31.2 m 3 per resident, see Figure 7.
Land 2023, 12,508 varied between 84.0% and 90.7% of residents. A similar situation may be not nized gas supply networks; currently, only 28.8% of the rural population (in to 72.3% of urban residents) has access to clean fuel, allowing to reduce the anthropopressure on the natural environment exerted by the fossil fuels used Figure 6 shows the time-related lengths of rural water and sewage ne annual investments in these systems' development. It is visible that the stat authorities were aware of the unsatisfactory development of rural sanitat combination with the outside financial support of the EU, significant inv sewage systems were provided, especially after 2009. The presented inves increased length of rural water supply systems may be correlated to the visi in water consumption by rural residents, from 22.6 m 3 to 31.2 m 3 per resident 7. Thus, the progress in rural sanitation development is evident (see also T there is still a lot of work and financial effort required. This statement is su data presented in Figure 5b, presenting the difference between population c water supply and sewage systems. In rural areas of Poland, over 40% of res  there is still a lot of work and financial effort required. This statement is su data presented in Figure 5b, presenting the difference between population c water supply and sewage systems. In rural areas of Poland, over 40% of re nected to water supply networks have no access to sanitary sewage and mu individual manners of sewage management and treatment on their own.  Thus, the progress in rural sanitation development is evident (see also Table 2), but there is still a lot of work and financial effort required. This statement is supported by data presented in Figure 5b, presenting the difference between population connected to water supply and sewage systems. In rural areas of Poland, over 40% of residents connected to water supply networks have no access to sanitary sewage and must organize individual manners of sewage management and treatment on their own.    Table 2).
The development of rural areas and their increased productivity (prese   Table 2).
The development of rural areas and their increased productivity (presented later in the text) result in increased energy consumption by the rural population. Figure 9 presents timerelated domestic electric energy consumption per one resident in rural communities related to total consumption in Poland combined with the share of renewable sources in the total energy production in Poland. During approx. the last two decades, the energy consumption by one member of rural populations increased by nearly 100%, from 431.9 kWh to 859.1 kWh (see also Table 2). Moreover, since 2014, the individual energy consumption in rural areas of Poland is higher than the total consumption in the country. It is visible that the increase in energy consumption during the last two decades was accompanied by the increase in the application of renewable sources to electric energy production but the achieved level, less than 20% of the total energy production in Poland, is rather low. Thus, the anthropopressure related to fossil fuels consumption may be significant, also in the rural areas. In comparison, according to Eurostat data, the mean usage of renewable sources for energy production in the European Union in 2020 reached the level of 37% [76]. The leading member countries in the EU used the following share of renewables in electric energy production: Austria-approx. 78%, Sweden-approx. 75%, Denmark-approx. 65%.
Land 2023, 12, 508 The environmental sustainability of rural regions may be also affected nicipal waste management. Figure 10 presents the number and area of rur waste landfill sites in rural Poland for the period 2004-2021. Both the numbe rural landfills available for waste deposition for the rural population reduce assessment period duration. The available data for Poland's population (no population are available in the GUS database) show that the total amoun wastes reduced from 237.1 kg/resident in 2004 to 216.7 kg/resident in 2021. the whole country, the selective collection of municipal waste is being perfo communities, i.e., in all communities in the country. Figure 10b also shows The environmental sustainability of rural regions may be also affected by the municipal waste management. Figure 10 presents the number and area of rural municipal waste landfill sites in rural Poland for the period 2004-2021. Both the number and area of rural landfills available for waste deposition for the rural population reduced during the assessment period duration. The available data for Poland's population (no data for rural population are available in the GUS database) show that the total amount of collected wastes reduced from 237.1 kg/resident in 2004 to 216.7 kg/resident in 2021. Moreover, in the whole country, the selective collection of municipal waste is being performed in 2477 communities, i.e., in all communities in the country. Figure 10b also shows the effective control of illegal waste dumping sites in Poland. Each year since 2008 (earlier data are unavailable), approx. 10,000-15,000 illegal sites have been liquidated, leaving approx. 2000-3000 of the observed existing sites as of 31 December. assessment period duration. The available data for Poland's population (no d population are available in the GUS database) show that the total amount wastes reduced from 237.1 kg/resident in 2004 to 216.7 kg/resident in 2021. the whole country, the selective collection of municipal waste is being perfo communities, i.e., in all communities in the country. Figure 10b also shows control of illegal waste dumping sites in Poland. Each year since 2008 (ear unavailable), approx. 10,000-15,000 illegal sites have been liquidated, lea 2000-3000 of the observed existing sites as of 31 December. The actual data presented in Figure 11 show negative anthropopressure exerted by Poland's agriculture on the natural environment, i.e., ammonia and greenhouse gas emissions from agriculture as the percentage of the total emission. Percentage agricultural emissions of ammonia in Poland is one of the highest in the European Union, 96.9%, while mean value for the EU is 90.9%. Only in Ireland and Cyprus, the percentage emission was higher in 2020, 99.2% and 97.3%, respectively, but both these countries have total and arable/agricultural area significantly smaller than Poland. On the other hand, the annual agricultural ammonia emission in Poland in 2020 reached the level of 21.1 kg per hectare and was clearly lower than the ones noted in Malta (123.3 kg/ha), Cyprus (62.7 kg/ha), the Netherlands (57.4 kg/ha) and Belgium (45.5 kg/ha). Contrarily, there are several countries in which agricultural ammonia emission is lower than or equal to approx. 10 kg/ha, i.e., Bulgaria, Estonia, Latvia, Romania and Greece. The percentage of agricultural greenhouse gas emission in Poland in 2020 was 9.1% and was lower than the EU mean value, 11.4%. Lower-percentage gas emissions in agriculture than in Poland were observed only among countries with significantly developed agriculture, such as in Belgium, Germany, Czechia, Italy and Slovakia. Thus, the above numbers showed than the ammonia fertilizers used in Polish agriculture may be the main source of anthropopressure exerted on the natural environment. This pressure may be reduced in future by an increase in area of organic farming, which (see Figure 12) in 2020 in Poland was equal to only 3.52% of total arable land and was far below the European Union mean-9.08%.
were observed only among countries with significantly developed agriculture, such Belgium, Germany, Czechia, Italy and Slovakia. Thus, the above numbers showed the ammonia fertilizers used in Polish agriculture may be the main source of anthr pressure exerted on the natural environment. This pressure may be reduced in futur an increase in area of organic farming, which (see Figure 12) in 2020 in Poland was e to only 3.52% of total arable land and was far below the European Union mean-9.08 Figure 11. Anthropopressure of agriculture in Poland and the EU in 2020, data from Eurostat (a) ammonia emissions from agriculture as % of the total emission, (b) greenhouse gas emis from agriculture as % of the total emission. The descriptive statistics of studied environmental Sustainable Development I cators values for the period under consideration are presented in Table 2.  The descriptive statistics of studied environmental Sustainable Development Indicators values for the period under consideration are presented in Table 2.

Social Sustainability
According to the available data, the number of rural residents was not constant and increased from 38.61% in 2004 to 40.32% in 2021 (see also Table 3), which meant 14,703,749 and 15,283,690, respectively. This increase in rural population may be related to the deurbanization of Polish cities caused by the migration of the middle class to single-family buildings located in the close vicinity of the major cities [66,67,[77][78][79]. Figure 13 presents the registered migration balance to and from rural settlements in Poland during the period 2004-2021. It is visible that over the studied period, the number of new registered rural residents was higher than the number of the population leaving rural settlements. during the period 2004-2021. It is visible that over the studied period, the nu registered rural residents was higher than the number of the population l settlements.    actual (i.e., 2021) mean life expectancy for the age class less than 1 year in the Eur Union is longer for both genders, i.e., 77.2 yrs. for males and 82.2 for females, th Poland. An indicator lower or comparable to Poland's life expectancy for newborn determined mainly in countries of the former Eastern Bloc, including Bulgaria, Rom Lithuania, Latvia, Hungary, Estonia and Czechia.    Table 3, the birthrate of the rural population decreased by over 140 The above-discussed changes in rural population are also reflected by the chang rural residents' age distribution, presented in Figure 16, for two years, the initial and year of this study, i.e., 2004 and 2021, respectively. It is visible that the number of chil from 0 to 6 years old is comparable. Then, the number of children and teenagers, years old, was clearly lower in 2021 than in 2004. The same observation is possibl young adults, i.e., 20-24 yrs. old. A different situation is visible in the case of adults seniors. The number of rural populations ranging in age from 35 to over 65 is great 2021 than it was in 2004. Thus, the rural population in Poland has become an agein ciety, with a significant share of people over 55 yrs., equal to approx. 28.9%. birthrate was noted for the rural population. The positive birthrate in the rural pop tion was stopped and diverted to negative values in 2019, after the beginning of COVID-19 pandemic. On the other hand, a positive birthrate in urban populations observed only in the short period between 2008 and 2011. Despite the governmental cial program "500+" [80] assuming extra financial support, initially for the second next children, later for all children, the total birthrate in Poland, in rural and as well a urban populations, decreased until the collapse in 2019. During the assessment durat as is presented in Table 3, the birthrate of the rural population decreased by over 1400 The above-discussed changes in rural population are also reflected by the change rural residents' age distribution, presented in Figure 16, for two years, the initial and f year of this study, i.e., 2004 and 2021, respectively. It is visible that the number of child from 0 to 6 years old is comparable. Then, the number of children and teenagers, 7 years old, was clearly lower in 2021 than in 2004. The same observation is possible young adults, i.e., 20-24 yrs. old. A different situation is visible in the case of adults seniors. The number of rural populations ranging in age from 35 to over 65 is greate 2021 than it was in 2004. Thus, the rural population in Poland has become an ageing ciety, with a significant share of people over 55 yrs., equal to approx. 28.9%.  Poland during the period 2004-2021 (see also Table 3). It is visible that the infant de indicator was on a comparable level in both groups and was significantly reduced dur assessment period duration. The discussed indicator decrease for residents of rural s tlements was from 6.35 to 3.31, while for urban residents it was from 7.14 to 3.96. Th the development of healthcare and improvement of living conditions since 2004, the trance of Poland to the European Union, is visible.     Figure 15 shows population dynamics, i.e., live births and deaths, for 1000 rural and urban residents combined with the birthrate for 1000 residents. During the studied period, the number of live births was higher in the rural population than in urban. Since 2014, the death rate was also lower for rural populations. However, since 2017, a decrease in live births for both studied regions occurred. Moreover, it is visible that since the outbreak of the COVID-19 SARS-Cov-2 pandemic, the number of registered deaths significantly increased, especially in the denser populated cities, from 10.92 deaths per 1000 residents in 2019 to 14.21 deaths per 1000 residents in 2021. The above observations are proven with the birthrate analysis presented in Figure 15b. The birthrates observed in rural and urban populations present comparable changes in time, but again, a higher birthrate was noted for the rural population. The positive birthrate in the rural population was stopped and diverted to negative values in 2019, after the beginning of the COVID-19 pandemic. On the other hand, a positive birthrate in urban populations was observed only in the short period between 2008 and 2011. Despite the governmental social program "500+" [80] assuming extra financial support, initially for the second and next children, later for all children, the total birthrate in Poland, in rural and as well as in urban populations, decreased until the collapse in 2019. During the assessment duration, as is presented in Table 3, the birthrate of the rural population decreased by over 1400%.
The above-discussed changes in rural population are also reflected by the changes in rural residents' age distribution, presented in Figure 16, for two years, the initial and final year of this study, i.e., 2004 and 2021, respectively. It is visible that the number of children from 0 to 6 years old is comparable. Then, the number of children and teenagers, 7-19 years old, was clearly lower in 2021 than in 2004. The same observation is possible for young adults, i.e., 20-24 yrs. old. A different situation is visible in the case of adults and seniors. The number of rural populations ranging in age from 35 to over 65 is greater in 2021 than it was in 2004. Thus, the rural population in Poland has become an ageing society, with a significant share of people over 55 yrs., equal to approx. 28.9%. Figure 17 presents another important SDI allowing assessment of life conditions and healthcare, the infant deaths per 1000 residents, for the rural and urban population in Poland during the period 2004-2021 (see also Table 3). It is visible that the infant death indicator was on a comparable level in both groups and was significantly reduced during assessment period duration. The discussed indicator decrease for residents of rural settlements was from 6.35 to 3.31, while for urban residents it was from 7.14 to 3.96. Thus, the development of healthcare and improvement of living conditions since 2004, the entrance of Poland to the European Union, is visible.
According to the available Eurostat data for 2013, see Figure 18, the annual farm labor force in Poland agriculture presented in full-time equivalents (FTEs) was second in the European Union with a result of 3,558,710 FTEs. Only Romania in 2013 noted a higher value of farm labor force, reaching 6,577,930 FTEs. Moreover, the physical work in Polish farms was performed mainly by family members, with 3,480,250 full-time equivalents giving 97.8% of the labor force.
According to the available Eurostat data for 2013, see Figure 18, the annual farm labor force in Poland agriculture presented in full-time equivalents (FTEs) was second in the European Union with a result of 3,558,710 FTEs. Only Romania in 2013 noted a higher value of farm labor force, reaching 6,577,930 FTEs. Moreover, the physical work in Polish farms was performed mainly by family members, with 3,480,250 full-time equivalents giving 97.8% of the labor force.     The summary of social Sustainable Development Indicators presented above is shown in Table 3.   The summary of social Sustainable Development Indicators presented above is shown in Table 3.  The summary of social Sustainable Development Indicators presented above is shown in Table 3.

Economic Sustainability
The issue of economic sustainability of rural regions may be assessed in several ways, by assessment of rural communities' incomes and expenditures, total agriculture productivity, as well by the selected economic indicators determined for the individual farmers. Figure 21a,b present total incomes of rural and urban communities, as local selfgovernments, combined with their expenditures (including also culture, education, heritage), for one resident, both for the studied period 2004-2021. It is visible that both incomes and expenditures of rural communities increased approx. by 302.8% and 270.6%, respectively, despite being clearly lower than incomes and expenditures of urban communities (see also Table 4). On the other hand, it is worth noting than the increase in expenditures per one resident of rural communities during the tested period exceeded the increase in expenses of the urban self-governments. heritage), for one resident, both for the studied period 2004-2021. It is visible that both incomes and expenditures of rural communities increased approx. by 302.8% and 270.6%, respectively, despite being clearly lower than incomes and expenditures of urban communities (see also Table 4). On the other hand, it is worth noting than the increase in expenditures per one resident of rural communities during the tested period exceeded the increase in expenses of the urban self-governments.  Figure 22 presents the annual mean disposable income per one residents in individual farming in Poland related to the mean income in self-employment during the studied time duration. The reported disposable income ratio was unfavorable for the individual farming throughout the whole period of assessment and varied between approx. 33.3 and 55.5% (see Table 4), reaching the bottom values in the recent period, i.e., 2019-21. Thus, individual farming in Poland is far less profitable than the other possible manners of self-employment. The above may be related to the fact that the dominant (52.5% of all farms) area of individual farms in Poland is smaller than 5 hectares [67].   Figure 22 presents the annual mean disposable income per one residents in individual farming in Poland related to the mean income in self-employment during the studied time duration. The reported disposable income ratio was unfavorable for the individual farming throughout the whole period of assessment and varied between approx. 33.3 and 55.5% (see Table 4), reaching the bottom values in the recent period, i.e., 2019-21. Thus, individual farming in Poland is far less profitable than the other possible manners of self-employment. The above may be related to the fact that the dominant (52.5% of all farms) area of individual farms in Poland is smaller than 5 hectares [67].
Unfortunately, the above disparity is also reflected in the mean monthly retirement in agriculture and in non-agriculture sectors, see Figure 23. During the entire duration of the studied period, the agricultural retirement, available to men over 65 yrs. and women over 60 yrs. (after at least 25 yrs.), of the contribution period [81] was significantly lower than in the other sectors and this difference increases. In 2004, the agricultural retirement was equal to 65.5% of the mean obtained in the other benches of activity. In 2021, the last year of assessment, this share decreased to 54.5% (see Table 4). Such a situation causes clear and visible unrest in the rural population, pressing for the reform of the agricultural retirement system in Poland [82][83][84][85].   Figure 22 presents the annual mean disposable income per one residents in individual farming in Poland related to the mean income in self-employment during the studied time duration. The reported disposable income ratio was unfavorable for the individual farming throughout the whole period of assessment and varied between approx. 33.3 and 55.5% (see Table 4), reaching the bottom values in the recent period, i.e., 2019-21. Thus, individual farming in Poland is far less profitable than the other possible manners of self-employment. The above may be related to the fact that the dominant (52.5% of all farms) area of individual farms in Poland is smaller than 5 hectares [67].  Unfortunately, the above disparity is also reflected in the mean monthly retirement in agriculture and in non-agriculture sectors, see Figure 23. During the entire duration of the studied period, the agricultural retirement, available to men over 65 yrs. and women over 60 yrs. (after at least 25 yrs.), of the contribution period [81] was significantly lower than in the other sectors and this difference increases. In 2004, the agricultural retirement was equal to 65.5% of the mean obtained in the other benches of activity. In 2021, the last year of assessment, this share decreased to 54.5% (see Table 4). Such a situation causes clear and visible unrest in the rural population, pressing for the reform of the agricultural retirement system in Poland [82][83][84][85]. One of the most important economic indicators of sustainable development relates to population at risk of poverty or social exclusion. According to Eurostat data for 2020, presented in Figure 24, 23.2% of the population in rural areas of Poland was in danger of poverty or social exclusion (a clear decrease in relation to 29.3% in 2015, see Table 4). This value is comparable with the EU mean (22.5%) but is higher than the indicator determined for the EUR currency zone (19.7%). At the same time, only 12.1% of the population of large cities in Poland were assumed to be at risk of poverty. On the other hand, the reported value for rural Poland is significantly lower than SDIs reported for Romania (50.1%), Bulgaria (42.5%) and Greece (34.0%). The lowest share of a rural population endangered by poverty or social exclusion was observed in Czechia (9.6%) and Austria One of the most important economic indicators of sustainable development relates to population at risk of poverty or social exclusion. According to Eurostat data for 2020, presented in Figure 24, 23.2% of the population in rural areas of Poland was in danger of poverty or social exclusion (a clear decrease in relation to 29.3% in 2015, see Table 4). This value is comparable with the EU mean (22.5%) but is higher than the indicator determined for the EUR currency zone (19.7%). At the same time, only 12.1% of the population of large cities in Poland were assumed to be at risk of poverty. On the other hand, the reported value for rural Poland is significantly lower than SDIs reported for Romania (50.1%), Bulgaria (42.5%) and Greece (34.0%). The lowest share of a rural population endangered by poverty or social exclusion was observed in Czechia (9.6%) and Austria (11.9%).
to population at risk of poverty or social exclusion. According to Eurostat data for 2 presented in Figure 24, 23.2% of the population in rural areas of Poland was in dange poverty or social exclusion (a clear decrease in relation to 29.3% in 2015, see Table 4). value is comparable with the EU mean (22.5%) but is higher than the indicator de mined for the EUR currency zone (19.7%). At the same time, only 12.1% of the popula of large cities in Poland were assumed to be at risk of poverty. On the other hand reported value for rural Poland is significantly lower than SDIs reported for Rom (50.1%), Bulgaria (42.5%) and Greece (34.0%). The lowest share of a rural population dangered by poverty or social exclusion was observed in Czechia (9.6%) and Au (11.9%). The general productivity of agriculture in Poland in relation to the remain member states of the EU is presented in Figure 25, showing gross value added for a culture in basic prices in 2020. The determined value of this indicator for Polish agr ture was EUR 12,103.63 million, which was approx. 5.5% of value for the EU and bec the fifth result, after France, Italy, Germany and Spain. The general productivity of agriculture in Poland in relation to the remaining member states of the EU is presented in Figure 25, showing gross value added for agriculture in basic prices in 2020. The determined value of this indicator for Polish agriculture was EUR 12,103.63 million, which was approx. 5.5% of value for the EU and became the fifth result, after France, Italy, Germany and Spain.
Land 2023, 12, 508 19 o Figure 25. Gross value added of agriculture at basic prices in the member countries of the E 2020, data from Eurostat [70].
The changes in productivity of Polish farming, as the main bench of agriculture, m also be represented by the agricultural production purchase by 1 hectare and structur products purchased per 1 ha-see Figure 26. The total value of Polish agriculture farm products purchase increased during the tested time duration from PLN 3674.00 to P 9046.00, which may be recalculated to approx. EUR 782-1925, without nearly unchan structure 43.0-43.8% of crops and 57.0-56.2% animal production. The farming prod purchase structure in 2021 was dominated by sugar beet, milk and grains. The changes in productivity of Polish farming, as the main bench of agriculture, may also be represented by the agricultural production purchase by 1 hectare and structure of products purchased per 1 ha-see Figure 26. The total value of Polish agriculture farming products purchase increased during the tested time duration from PLN 3674.00 to PLN 9046.00, which may be recalculated to approx. EUR 782-1925, without nearly unchanged structure 43.0-43.8% of crops and 57.0-56.2% animal production. The farming products purchase structure in 2021 was dominated by sugar beet, milk and grains. The changes in productivity of Polish farming, as the main bench of agriculture, may also be represented by the agricultural production purchase by 1 hectare and structure of products purchased per 1 ha-see Figure 26. The total value of Polish agriculture farming products purchase increased during the tested time duration from PLN 3674.00 to PLN 9046.00, which may be recalculated to approx. EUR 782-1925, without nearly unchanged structure 43.0-43.8% of crops and 57.0-56.2% animal production. The farming products purchase structure in 2021 was dominated by sugar beet, milk and grains.  Figure 27 presents energy productivity in the member states of the EU, determining the amount of economic output that is produced per unit of gross available energy in EUR per kg of oil equivalent, shows that productivity in Poland, including agriculture, is one of the lowest in the EU. The determined value of 4.72 EUR/kg oil equivalent is higher only than indicators reported for Estonia, Czechia and Bulgaria and is definitely lower  Figure 27 presents energy productivity in the member states of the EU, determining the amount of economic output that is produced per unit of gross available energy in EUR per kg of oil equivalent, shows that productivity in Poland, including agriculture, is one of the lowest in the EU. The determined value of 4.72 EUR/kg oil equivalent is higher only than indicators reported for Estonia, Czechia and Bulgaria and is definitely lower than the mean EU value of 8.57 EUR/kg oil equivalent. However, it worth noting that in 2004, the energy productivity in Poland was even lower, 3.02 EUR/kg oil equivalent.  The general economic sustainability of rural areas in Poland may be also reflected by the governmental funds granted to agricultural research and development (R&D), allowing to assess how much priority is placed on R&D by state budget fund allocations. Figure 28, presenting governmental support for R&D activities in agriculture in Poland in 2020, shows that the sum of EUR 3.8 per resident is far below the mean EU value equal 7.2 EUR/resident. This value is also several times lower than in countries significantly supporting agricultural R&D, i.e., Ireland, Denmark, the Netherlands, Germany and Finland. However, it is worth mentioning than in 2004, the budget allocation for agricultural research and development in Poland was equal only to 0.1 EUR/resident (see also Table 4). The general economic sustainability of rural areas in Poland may be also reflected by the governmental funds granted to agricultural research and development (R&D), allowing to assess how much priority is placed on R&D by state budget fund allocations. Figure 28, presenting governmental support for R&D activities in agriculture in Poland in 2020, shows that the sum of EUR 3.8 per resident is far below the mean EU value equal 7.2 EUR/resident. This value is also several times lower than in countries significantly supporting agricultural R&D, i.e., Ireland, Denmark, the Netherlands, Germany and Finland. However, it is worth mentioning than in 2004, the budget allocation for agricultural research and development in Poland was equal only to 0.1 EUR/resident (see also Table 4). Figure 28, presenting governmental support for R&D activities in agriculture in Poland in 2020, shows that the sum of EUR 3.8 per resident is far below the mean EU value equal 7.2 EUR/resident. This value is also several times lower than in countries significantly supporting agricultural R&D, i.e., Ireland, Denmark, the Netherlands, Germany and Finland. However, it is worth mentioning than in 2004, the budget allocation for agricultural research and development in Poland was equal only to 0.1 EUR/resident (see also Table 4). Figure 28. Governmental financial support for agricultural research and development in the member states of the EU, 2020, data from Eurostat [70].
Economic sustainability of the rural population in Poland may be, as is reported for other regions [86][87][88], improved by additional activities including offering an accommodation base for agritourism. According to the official regulations in Poland, agritourist accommodation is understood as facilities where hotel services may be provided, including rooms or tent sites, rented from farmers on farms run by them [89]. Figure 29 presents the number of agritourist facilities available in Poland in the period 2012-2022 and the percentage of use of the accommodation. The number of registered facilities constantly decreased since 2015, from a value of 811 facilities with 13, 351 places to 583 facilities with 10,440 places. The highest decrease was noted for the COVID-19 pandemic duration, since 2019. However, the number of clients using the available accommodation, besides COVID-19 pandemic duration, was not reduced so clearly, which is reflected in Figure 28. Governmental financial support for agricultural research and development in the member states of the EU, 2020, data from Eurostat [70].
Economic sustainability of the rural population in Poland may be, as is reported for other regions [86][87][88], improved by additional activities including offering an accommodation base for agritourism. According to the official regulations in Poland, agritourist accommodation is understood as facilities where hotel services may be provided, including rooms or tent sites, rented from farmers on farms run by them [89]. Figure 29 presents the number of agritourist facilities available in Poland in the period 2012-2022 and the percentage of use of the accommodation. The number of registered facilities constantly decreased since 2015, from a value of 811 facilities with 13, 351 places to 583 facilities with 10,440 places. The highest decrease was noted for the COVID-19 pandemic duration, since 2019. However, the number of clients using the available accommodation, besides COVID-19 pandemic duration, was not reduced so clearly, which is reflected in increased use of accommodation. Thus, it seems to be clear that the development of agritourism may be beneficial for the improvement of economic conditions of rural populations, especially in the numerous environmentally attractive regions of Poland-mountains, seaside and lake districts.  A summary of the studied economic Sustainable Development Indicators for the time duration under consideration is presented in Table 4. Rural population at risk of poverty or social exclu- A summary of the studied economic Sustainable Development Indicators for the time duration under consideration is presented in Table 4.

Discussion
The performed survey of time-related changes in the values of the proposed set of Sustainable Development Indicators for rural areas of Poland since 2004 and analyses of the determined percentage indicator value changes showed a clear progress in numerous aspects of development during the assessment period. The positive changes in rural Poland's environmental, social and economic growth reported by several studies since the second decade of the 21st century [42,[53][54][55][56]59,62] were sustained. However, in many cases, the discussed values are far below the ones indicated for the leading European countries or even the mean for 27 member states. Additionally, as was mentioned before, the generally globally recognized limits to the sustainable development of rural regions, including issues of anthropopressure exerted by agriculture on the natural environment, limited access to resources and basic services, including water and sanitation, depopulation and the socio-economic gap between rural and urban regions, even leading to poverty and social exclusion [43][44][45][46][47][48][49][50][51][52], may be recognized in the results of the presented survey.
According to data presented by the Polish Inspectorate of Environmental Protection the first free water table groundwater aquifer, supplied by infiltration water, is more endangered by pollution than the confined aquifers. The main described cause of unsatisfactory or bad groundwater quality determined for studied cases exceeded the quality threshold values, mainly for the following indicators: K (15 mg K/dm 3 ), B (1 mg B/dm 3 ), NO 3 (50 mg NO 3 /dm 3 ), NH 4 (1.5 mg NH 4 /dm 3 ) and SO 4 (250 mg SO 4 /dm 3 ). Disorganized water and sanitary sewage management, inappropriate municipal waste management, as well as the road transport-related issues, combined with the insufficient isolation of the groundwater table from infiltrating surface water, were recognized as the main reasons for groundwater pollution in rural areas of Poland. Similar observations were reported for other countries all around the world [45,[90][91][92][93][94]. However, it should be mentioned that according to several scientific reports, construction and operation of organized rural sewage systems under actual conditions in Poland is unprofitable and financially ineffective, which may result in a low level of rural population acceptance and willingness to pay [67][68][69][95][96][97][98][99][100][101][102]. The individual devices of sanitary sewage management and treatment, as an alternative to costly organized systems, became popular in Poland after 2009, when a clear increase in their installation was observed. This popularity may be highly related to the possible higher economic profitability and cost-efficiency of the individual manners of sewage management and treatment under the conditions of rural Poland [95,96].
The increased domestic tap water demand may be significantly reduced, even by approx. 50%, by replacing drinking water by non-potable water collected by rainwater harvesting (RWH) systems and used in toilets and laundry facilities, cleaning, garden irrigation and washing vehicles [103][104][105][106][107]. However, the performed research [108] concerning application of 13 various designs of RWH for single-family buildings under the climatic and economic conditions of Eastern Poland showed that, in most cases, such designs are unprofitable for the investors. Moreover, the available governmental funding support for RWH devices covering two programs for the area of the quoted study was insufficient, allowing to refund from 50% to 100% of costs but only to the value of approx. EUR 660-1100 per installation. Such state co-funding was, in many studied cases, insufficient, especially for the sophisticated, up-to-date and complex systems of collection, storage, treatment and reuse of rainwater (the actual cost of just one rainwater control station purchase in Poland varies between EUR 650 and 1400) [109,110] may be also related to air pollution. According to the actual official mandatory register of heat sources in the residential buildings in Poland [111], covering in total 13,764,724 heat sources, the dominant sources are solid fuel boilers and ovens (55.20%), gas boilers (23.79%), electric heating (11.74%), municipal sources (3.11%), solar panels (2.99%), heat pumps (2.18%) and oil boilers (0.99%). The same source identifies the soiled fuels used in residential buildings in Poland as coal (55.6%), wood (37.4%), wood pellet (6.1%) and other biomass (0.8%). According to the data by the Polish Ministry of Climate and Environment, in 2020, there were 67,300 geothermal heat pumps installed in the whole country. During the 2018-2021 program "Clean air" of heat source replacement in Poland, covering 296,653 heat sources, only approx. 17% of zero-emission air and ground-source heat pumps were installed, 13.95% and 3.31%, respectively [112]. Thus, low installation costs and quick-assembly heating devices are preferable by individual investors, so application of the low-temperature geothermal sources of heating energy is highly undeveloped.
The analysis of social development indicators presented above shows that rural society in Poland encounters problems typical for similar populations, not only in new member states (since 2004) of the European Union, but also visible for the other Eastern European countries [42,50,52,55,[60][61][62][113][114][115][116][117][118]. These issues are depopulation and the ageing of the rural population, negative birthrate, shorter life expectancy than in urbanized regions Land 2023, 12, 508 23 of 29 and significant workload required for agriculture. The observed improvement of sanitary conditions of the rural population in Poland and available healthcare, related not only to previously discussed environmental sustainability indicators, but also visible by the significant decrease in infant deaths per capita, was, in confrontation with the COVID-19 SARS-CoV-2 pandemic, insufficient to prevent the negative changes in rural population demographics. However, in this case, the economic factors including, inter alia, low agricultural disposable income, low retirement and relatively low productivity of agriculture combined with the high energy consumption, creating a visible gap between the economics of rural and urban populations, may affect both the social and economic development of the rural population, despite the observed positive trends [46,62,[119][120][121][122][123]. It is worth mentioning that the development of an agritourist accommodation base in Poland's countryside, despite also being affected by COVID-19 lockdowns, presents a clear example of economic opportunity outside the traditional agriculture sector, similar to the wide touristic potential of other countries [86][87][88].
To summarize the discussion, we may state that, in our opinion, the following limits to the sustainable development of rural areas in Poland during the period 2004-2021 may be identified in the three studied circles of sustainability: Relatively high value of labor force, provided mainly by the family members of the farm owner, reflects low productivity of Poland's agriculture.

3.
Economic sustainability limits -Unfavorable economic conditions of rural population, leading to the significant risk of poverty and social exclusion, reflected by i) low value of disposable income in agriculture (far less than 50% of disposable income in self-employment in different sectors), ii) low monthly retirement in agriculture. -Lower incomes and expenditures of rural self-governments in relation to urban areas. -Low productivity of Poland's agriculture reflected by low gross value added to agriculture and low energy productivity. -Very low value of governmental support to agricultural research and development.

Conclusions
The performed analysis of Sustainable Development Indicators for rural areas in Poland since 2004, based on the proposed set of 38 indicators of environmental, social and economic development, allowed the following conclusions: - The environmental, social and economic development of rural areas of Poland since 2004, understood as positive changes in values of studied sustainability indicators, is clearly visible. -However, in many cases, the actual values of the studied Sustainable Development Indicators are below the mean for the European Union and are sometimes several times worse than in the case of the leading EU countries.
-There is also a visible difference between the values of numerous sustainability indicators determined for the rural and urban regions of Poland, showing that rural settlements develop slower. -Several serious threats limiting the sustainable development of the rural areas and agriculture in Poland were identified, affecting availability of natural resources, limiting the economic profitability of agricultural production and the stable social growth of rural population. -In many cases, state intervention is required to sustain the development of the rural population in Poland, mainly by increased productivity and development of agriculture, limiting risk of poverty and social exclusion, as well as allowing the improvement of rural population demographics. -Financial support for local domestic installations of rainwater harvesting allowing a significant reduction in tap water demand by offering treated rainwater should also be provided. -Governmental support is also required in development of individual off-grid renewable energy sources and providing clear energy for heating, significantly reducing the anthropopressure exerted on the natural environment by burning fossils. - The development of non-agricultural economic activities by the rural population, including agritourism, should also be encouraged and supported by the state.