Land footprint: theory, methodology, and applied ecological-economic principles in Ukraine

This article justifies methodological approaches to determine the land footprint using scientific research on ecological, water, and carbon footprints. Foreign scholars define the land footprint as the amount of land used to produce goods until the products are finally consumed in another country or region. This means that the system can account for the relocation of production to other parts of the world. In Ukraine, several indicators have been proposed to assess the ecological consequences of agricultural land use. They allow for monitoring, control, and prediction of changes in land, identifying crisis situations in agricultural land use. In our opinion, them should be use to characterize the «land footprint». The article analyzes the ecological consequences of the reorientation of Ukrainian producers exclusively on the market demand of grain crops for the purpose of export. It establishes that in adapting agricultural production to market conditions in Ukraine, a new land use system has formed, which benefits large landowners, preference is given to market-driven grain and technical crops, an increased burden on land resources, their depletion is occurring, and negative values of the «land footprint» are observed from such land use.


Introduction
The continuous growth of the global population, decreasing crop yields due to global warming and climate change, and the reduction of high-productivity arable land area create conditions for an increase in demand and prices for food.At the same time, increasing production volumes through further intensification of agriculture will have catastrophic environmental consequences, as it is a significant pollutant of the natural environment.

Related works
In scientific circles and statistics in recent years, a large number of methodologies related to the «ecological footprint» indicator, associated with ecological and water resources, food consumption, greenhouse gas emissions, and so on, have been presented.However, there is still no agreed-upon methodology for calculating these indicators in the context of resource efficiency.Furthermore, the 1269 (2023) 012004 IOP Publishing doi:10.1088/1755-1315/1269/1/012004 2 availability and quality of data for calculating various footprint indicators vary depending on the methodology and calculation methods for different natural resources.
The term «footprint» was first introduced by W Rees and M Wackernagel [2], in the early 1990s when they first introduced the «ecological footprint» indicator for quantifying the biological productivity of territory necessary for assimilating waste at global or national scales [5,23].Since its introduction, the term «footprint» has been used in many other concepts of ecological accounting, including global climate policies related to greenhouse gases on a global scale [6].More recently, the term «footprint» has also been introduced for indicators related to water consumption, materials, and the overall impact of products on natural resources.
The ecological footprint is a composite indicator that illustrates the total amount of land and water necessary for humans, populations, or activities to produce all the resources they consume and to absorb the waste they generate [24].The ecological footprint typically includes all territories necessary to satisfy consumption within a certain country, including those embodied in international trade.Accounting for the ecological footprint takes into consideration space for raw material production (agricultural crops, land quality, etc.), territory for absorbing greenhouse gases, water arteries for diluting and purifying wastewater, and so on.
The growth of the population and economic income forces us to consider land footprint as an important factor for balanced societal development [25].Additionally, Europe is the continent that relies the most on imported land.Today, the EU is already a «net importer».In particular, six out of the top 10 countries that import the most through the «virtual land» indicator are Germany, the United Kingdom, Italy, France, the Netherlands, and Spain.Germany and the United Kingdom import nearly 80 million hectares per year [3].Compared to the available arable land per capita worldwide, the EU uses approximately one-third more than the global average.
The land footprint typically assesses those land areas that are directly or indirectly necessary to satisfy consumption or the production of specific products or overall consumption.This is a powerful method for illustrating the dependence of local territories (regions or countries) on foreign land, which is embodied in imports and exports («virtual land») [26].
Another definition and use of the land footprint involve it being equivalent to the ecological footprint, excluding land for carbon absorption since it is directly related to CO2 emissions already captured [8].Additionally, it is defined as the amount of biologically productive land required to satisfy consumption [7].Currently, there is no agreed-upon definition of the land footprint [25].It's important to note that approaches to defining the land footprint differ from ecological footprint calculations because they do not weigh land areas by varying biological productivity.K Erb used yield indicators for individual countries to determine the actual demand for land in Austria and showed that during the period from 1926 to 2000, Austria was a net importer of arable land [27].M Kissinger and W Rees identified productive land embodied in USA imports during 1995-2005 and found that in the globalized world, even countries capable of meeting most of their needs are becoming more dependent on and influential in external terrestrial ecosystems [9].M Fader quantitatively calculated the balance of virtual land in international trade in agricultural crops and found that the USA, Canada, Argentina, and Australia are net exporters of virtual land [10].
Therefore, the methodology for calculating national land footprints combines data on land use from the Food and Agriculture Organization and trade data from the Global Trade Analysis Project [28].This methodology allocates the amount of land used to produce goods to the country where the products are ultimately consumed.It takes into account the amount of land needed for production (e.g., the land needed for animal husbandry intended for meat consumption) as well as the amount of land in each country and imported from other countries.This means the system can account for the relocation of production to other parts of the world.The EU is gradually obligating food producers to take specific actions regarding land use safety, nature protection, and sustainable development.In our opinion, to characterize the «land footprint», both quantitative and qualitative indicators should be used, describing changes in the ecological and agrochemical state of land due to agricultural production.Ukrainian scientists have been studying this issue for a long time, and as a result, they have developed and tested various methodologies for the ecological assessment of agricultural land.These methodologies enable monitoring, control, and forecasting of changes in the functioning of agrolandscapes, identifying crisis situations in agricultural land use, and serve as an information base for making management decisions regarding the formation of sustainable land use, conservation, and reproduction of the natural resource potential of agricultural land, and improving their use efficiency.
The methodology for qualitative soil assessment (land rating) by A I Siruy is based on soil fertility criteria [29].V Medvedev proposed an improved methodology for assessing the suitability of an entire complex of natural-climatic conditions and technological features of a specific field (a single system of «soil-climate-field») for the cultivation of agricultural crops [30].Methodological approaches for assessing the scale of soil degradation were developed by specialists [31].The methodology for the comprehensive assessment of the agroecological condition of agricultural lands proposed by O Rakoyid takes into account the eco-agrochemical condition of arable land and the degree of disturbance of their ecological balance [32], assessment of ecological safety and agroecological condition of arable lands [33].Assessment of environmental safety and the agroecological condition of arable land is also legislated in Ukraine, with periodic assessments of soil quality (every 5 years for arable land) [34].
In conclusion, a series of indicators have been proposed to assess the ecological consequences of agricultural land use, including soil suitability score, anthropogenic load coefficient, ecological stability coefficient, plowing coefficient, level of agricultural development, an integral indicator of land ecological condition, and ecological safety index.However, they have never been used to assess or measure the «land» footprint.
Land resources are of strategic importance for ensuring food security and economic growth in Ukraine.Therefore, researching the impact of modern agricultural land use on soil conditions and the need to develop recommendations for ensuring ecological-economic security and high efficiency of their utilization remains relevant for Ukraine.Considering the fact that our country is a leading producer of food grains and fodder, preserving the quality of Ukrainian soils is essential for global food security.

Method
The research is based on general scientific research methods.The historical method was used to investigate the origin and usage of the concept of «footprint».Statistical methods were employed in collecting, processing, and analyzing information regarding the structure and quantity of crop areas.A systemic approach was applied to determine the role of land resources in Ukraine's economic development and global food security.Using the comparative method, advantages and disadvantages of existing footprint calculation methods were identified.Analysis and synthesis methods were utilized during the measurement of the «land» footprint.The conclusion formation process involved the method of generalization.

Results and discussion
Based on contemporary scientific developments, the following definitions have been formulated for four footprint indicators.Material footprint reflects the quantity of global material used throughout the entire life cycle of a product and is related to a country's final consumption.Thus, the material footprint is a new term and pertains to the life cycle of material resources in products [35,36].Material footprints can focus on the extraction of used material (reflected by the indicator of raw material consumption) or material consumption (overall material consumption).The methodological approaches to calculating the material footprint, according to major recommendations from EUROSTAT [37] or OECD [38], are already being used worldwide.
Water footprint represents the total amount of freshwater used directly or indirectly in the production of goods and services for a country's final consumption.In recent years, the number of scientific developments and publications related to water footprints has increased significantly, covering topics such as water basins, a country's «green» GDP, various countries and industries, and food production.[31 -33].
It is important to note that approaches to land footprint differ from ecological footprint calculations, as they do not consider land areas weighted by varying biological productivity.Unlike the material footprint, there is currently no agreed-upon definition of the land footprint.Due to data limitations, land footprint studies are still often used in agriculture and forestry.Land footprint is typically expressed in hectares or square meters (m2).Land footprint considers only direct land use and does not include the carbon footprint.
Overall, there are three types of methodologies for calculating a specific category of footprint.The first group of approaches is based on various forms of cost-benefit analysis and results that combine physical data on resource usage (material, water, land) or emissions (greenhouse gas emissions in the case of the carbon footprint).The «cost-benefit» analysis is a top-down approach, meaning it begins the assessment at the macroeconomic level (the entire economy) but includes sectoral breakdowns.One of the most important applications of «cost-benefit» analysis is calculation of total costs per unit of final product.Using such a methodology the allows us to assess not only direct costs in the production process within a specific sector but also all indirect costs that occur during the supply of intermediate products from other sectors [17,20,21,39].
The key advantage of coefficient approaches, compared to the "cost-benefit" approach, is their high level of detail and transparency.Coefficient approaches do not face limitations by sectors, allowing for comparisons at the level of individual products or materials [4].Hybrid approaches are the third major type of methodologies that combine elements of both cost-benefit analysis and coefficient approaches.Therefore, a hybrid approach will be an essential tool for future methodological development concerning the footprint indicator.The key advantage of the hybrid approach is that the applied coefficients compensate for the shortcomings typically encountered when using the "cost-benefit" approach [17,18].What's particularly attractive is that such a hybrid approach allows for calculating footprints for four major resource categories (land, water, greenhouse gases, materials) using the same analytical toolkit.
Therefore, hybrid approaches have a very high potential since they combine the advantages of both main methods.In our opinion, this method is widely used in practice today and the most socioecologically-economic feasible, socially necessary, and environmentally justified method.It takes into account various processes (production, managerial, societal).
The agricultural land footprint is the area of land (in hectares) used to produce a crop yield (in kilograms).In other words, the agricultural land footprint determines how much land is required for a particular agricultural crop, either in absolute terms or in relative terms when compared to a reference footprint for that crop [40].
The land footprint is the actual amount of land, wherever it may be, needed for the production of a product or used by an organization or nation.The land footprint is a systemic indicator of land resource use in the life cycle theory, required for the production of a product or used by an organization or nation, and is determined as a quantity inversely proportional to crop yield: where: LFland footprint of a crop, m²/kg; Y -yield, €/ha.Source: author's development.
The land footprint can be calculated at various levels: micro-level (individual economic entities), meso-level (basin level, administrative units), and macro-level (entire countries).When deciding which crops to cultivate, farmers will be guided by economic aspects regarding the rational use of water and land resources used in their economic activities.However, optimizing the use of water and land at the farm level can lead to significant overall water and land footprints at the level of a watershed, disrupting resource sustainability.Therefore, when making decisions at the micro-level, it is essential to consider the impact at the basin, country, and global levels.
Economic Land Productivity (ELP, €/m²), from an economic perspective, demonstrates how much money corresponds to each square meter of land used in economic activities.Micro-level considerations focus on the efficiency and productivity of land resource utilization by individual farming enterprises or other economic entities.At the macro-level, the sustainability and socio-ecological-economic appropriateness of land resource use (river basin, country, world) are evaluated.
The overall land footprint at the system level is the result of the impact on land resources of all components of the system.At the macro-level, efforts are typically made to quantitatively determine critical limits (assimilation capacity) of overall pressure in the system to maintain the stability of land resources [14,22,41].Exceeding these limits will lead to undesirable consequences.Determining the most stable footprints is one way to quantitatively assess the critical use of land resources at the macrolevel [42].To ensure socio-ecological balance in natural-economic systems, the most environmentally sound, socially necessary, and economically justified land-use technologies need to be applied.
To measure socio-ecological-economic products (footprints, including land), both existing territorial-economic systems (communities) and theoretically possible (ecologically certified territorialeconomic systems), the following formula can be efficiently used (author's development based on [42]): ( where: SEE -Total Socio-Ecological-Economic Product of a territorial-economic system (community); Sfact., Steor.actual and theoretical volumes (quantity of products, services) in the social sphere, respectively; Efact.ecol., Eteor.ecol.actualand theoretical volumes (quantity of products, services) in the ecological sphere, respectively; Efact.econ., Eteor.econ.actualand theoretical volumes (quantity of products, services) in the economic sphere; K1, K2, K3coefficients of the importance of social, ecological, and economic products in territorial-economic systems.
The formula demonstrates a systemic approach to determining the land equivalent ratio for the comprehensive measurement of agricultural production efficiency on the scale of territorial-economic systems (communities).The formula is based on the concept of a yield gap, i.e., the ratio of the actual volume of agricultural production to the potential volume that could be obtained from one unit of land area.This methodology considers not only the crop yield but also the provision of services of all kinds on all land parcels forming a single landscape (a unified territory, system, or currently a community).The methodology encompasses all services relevant to any specific context, considering weighting coefficients determined by the importance to respective stakeholders (societal weighting coefficients).Consequently, there may be a need to aggregate weighting coefficients by scales and groups of stakeholders who may assess the importance of the same services differently.
Ukraine's agriculture during the period of martial law is facing rather challenging times, despite having a substantial land potential that is being underutilized.The government of Ukraine should diversify the current agricultural portfolio away from low-value, staple crops to increase overall productivity, reduce risks of crop failure, drought, market volatility, and consequently, boost exports of processed products (semi-finished goods).
During the process of adapting agricultural production to market conditions, significant changes have occurred in the land use system.Producers have shifted their focus solely to market demand (primarily for export), leading to a decline in livestock farming in the country.The lack of effective state control over land users with private ownership has completely disrupted the scientifically substantiated and proven land use system.In particular, there has been a significant change in the structure of arable land and the list of crops in crop rotation.Over the last 50 years, Ukraine has gone through several stages of land use evolution: planned improvement of soil quality until 1990; exhaustion of potentially most fertile soils (1990 -2010); the beginning of involving less fertile lands (cultivation of lands that were practically unused in 1990-2010); intensification of land use and specialization in grain and industrial crops with geographic expansion of sunflower and rapeseed cultivation in the northern regions of Ukraine (from 2010 to the present).
The analysis was conducted using the example of Rivne Oblast, which is located in the Polissia and Forest-Steppe zones over the past 30 years.As seen in Fig. 1, the sown area has decreased by almost half.This process has been observed from 1990 to 2014, partly associated with changes in the legal framework, transitioning from collective to private ownership, and the development of small-scale and family farming.However, the main reason was the removal of less fertile and 'problematic' lands from cultivation, which constantly require additional capital expenditures for liming, maintenance of reclamation structures, reclamation, etc.
After 2014, the sown areas in the region have been growing at a slow pace, primarily due to the consolidation of land holdings by agro-holdings.They absorb small farming іn addition, the structure of cultivated areas has also changed.For example, the share of fodder crops in the structure has decreased from 37.5% in 1990 to 2.2% in 2020; the cultivated areas of sugar beet and barley have halved, and flax cultivation has virtually ceased.Today, due to their high value and export potential, high-profit technical crops are grown in their place.For instance, over the past 10 years in Rivne Oblast, the area under soybean cultivation has increased tenfold, corn by five times, and sunflower by 22 times (Figure 2, 3).[43] An analysis of land use data in Rivne Oblast, considering the Polissia and Forest-Steppe zones over the past 30 years, was conducted.Specifically, in the Polissia zone of Rivne Oblast, there has been a consistent trend of reducing wheat cultivation since the 2000s.Today, wheat is sown in Polissia 10 times less than in 1995, 4 times less than in 2000, and 2 times less than in 2005.Over 15 years, the area under buckwheat has decreased by 5 times, and barley by times.Crops like sugar beet, corn, and flax have virtually stopped being grown on an industrial scale due to low efficiency.In contrast, natural land reclamation and afforestation processes have expanded.Starting from 2013, the area under soybean cultivation has been increasing every year (annual growth rate of 150-200%) as well as sunflower (400% growth) over the past five years.Rapeseed is still being cultivated, but its areas are smaller than in the 90s.
In the Forest-Steppe zone, where the soil quality is relatively better, a high level of soil erosion is maintained.However, over the past 10 years, there has been a trend of reducing the area under wheat by 25%, buckwheat by 60%, barley by 25%, corn by 15%, and winter rye and millet are virtually not grown anymore.The areas under vegetable crops, fodder crops, annual and perennial grasses are approaching zero.The trend of constant growth in cultivated areas is observed only for some technical crops, such as soybean (13 times) and sunflower (7 times) over the last 10 years.
An important socio-ecological-economic aspect of such land use systems is the failure to account for the ecological (natural) component in determining the cost of agricultural products.Profits obtained from high yields are attributed to today, while costs are left for future generations.
In order to improve the economic evaluation of land resources used in the cost of agricultural production, we proposed calculating the «land footprint».In our opinion, the volume of water consumption for the cultivation of 1 ton of products indicates the 'water footprint'; the sum of emissions of all greenhouse gases formed directly and indirectly as a result of the cultivation (production) of 1 ton of products is referred to as the 'carbon footprint'; the amount of basic nutrients (NPK) and humus used for the cultivation of 1 ton of products indicates the «land footprint».
If, during the cultivation of a crop, a positive or at least «0» balance of NPK and humus has been ensured, then such activity is considered not to leave a 'land footprint' behind.All expenses to achieve this are included in the cost of production.If the situation is opposite, and the natural reserves of land resources were used for crop production without subsequent compensation, then this type of land use leaves a negative «land footprint».In this case, the cost of production is reduced due to the depletion and depreciation of land resources, and the compensation for the incurred losses is shifted to the future, to the next land user or generation 30 years.The magnitude of the incurred losses and the one-time profits are incomparable, especially considering the time factor required to implement restoration measures even with available financial resources.Therefore, controlling the 'land footprint' of agriculture today is essential for the country's economic, ecological, and food security in the future.The analysis of the dynamics of changes in the structure of cultivated areas has shown that in 2020, the top 5 crops (corn for grain, soybean, winter wheat, sunflower, and rapeseed) occupy 83% of the cultivated area.In 1990, the leaders were winter wheat, corn for silage, spring barley, winter rye, and sugar beet, and their share was 56%.This indicates a disruption of crop rotation.
To assess the impact of changes in land use structure and crop rotation, we have calculated and compared the 'land footprint' for the years 1990-2020.To do this, we will calculate the average yield of major nutrients (NPK) and humus mineralization in the formation of the yield from a conditional 1 ha with a certain structure of cultivated areas using the formula: where: Harvestgross harvest of crops, t/ha; NNPKnorms of essential nutrient removal per 1 ton of main products; Ptotaltotal cultivated area, ha.Source: author's development.
Similarly, we will calculate the average yield of humus.
where: Pіcultivated area under a crop, ha; Міhumus mineralization under different crops.Source: author's development.
Nutrient removal from soil by agricultural products is the amount of nutrients spent on the formation of the entire biomass of the crop and is extracted from the field together with the main or main and byproducts after its removal from the field.The value of the Nutrient Utilization Coefficient from the soil depends on the crop, its biological characteristics, yield, soil, and technology.Therefore, this indicator best represents the «land» footprint of agricultural land use.The calculations of the land footprint are shown in Figures 4 and 7.As seen in Figure 4, in 2020, the yield of nitrogen (N) increased by 34%, and phosphorus (P) increased by 86% compared to 1990, while the yield of potassium (K) decreased by 40%.
Similar calculations were conducted for the Polissia and Forest-Steppe zones based on data from Kostopil and Radiviliv districts, respectively.The results of the calculations are shown in Figures 5, 7.
From the figures, it is evident that in the Polissia zone, there were trends of increasing nitrogen and potassium yields until 2011, after which there was a decrease in the yield of all essential nutrients due to reduced intensity of using less fertile Polissia soils.Today, the substantial increase in agricultural production is indicated by a 3-fold increase in nutrient removal from the soil in 2020 compared to 2011.As seen in Figure 5, in 2020, the yield of nitrogen increased by 22%, phosphorus by 100% compared to 1990, while the yield of potassium decreased by half.Source: compiled and calculated by the authors based on [43,45].
As seen in Figure 7, the level of humus mineralization has been steadily increasing since the early 2000s and currently averages 1.42 t/ha, which is 13% higher than in the 1990s and 22% higher than in the 2000s in Rivne region (Figure 5).The level of humus mineralization has been steadily increasing since the 1990s and currently averages 1.39 t/ha, which is 18% higher than in the 1990s in the Forest-Steppe zone.The increase in humus mineralization rates in the Polissia zone can be explained by the expansion of soybean, sunflower, and maize cultivation, which were not previously common in this zone.The level of humus mineralization currently averages 1.44 t/ha, which is 17% higher than the level of the 1990s.
Therefore, in the process of adapting agricultural production to market conditions, a new land use system has been formed within the country.The reorientation of Ukrainian producers solely towards market demand (especially for export), the decline of animal husbandry, the absence of effective state control over land users with private ownership, have completely disrupted the scientifically grounded and tested land use system.The existing model of agribusiness benefits only a few while harming the majority, such as small farmers, who have been the backbone of the food security and production system in rural areas for millennia.They face problems due to soil degradation and the globalization of the food system.Preference is given to concentrated, large-scale, and highly mechanized farming operations.As a result, the structure of cultivated areas has changed, recommended crop rotations have been violated, and the application of organic and mineral fertilizers has decreased.Monoculture cultivation predominates, ignoring drainage measures, leading to increased pressure on land resources, their depletion, and a negative 'land footprint' from such land use.

Figure 7.
Dynamics of humus mineralization in Rivne region, t/ha.Source: compiled and calculated by the authors based on [43,45].

Conclusions
The authors suggested that together with the concepts of "ecological", "carbon" and "water", the concept of "land footprint" should be used to assess the effects of human economic activity on the natural environment, in particular, agricultural land use on agricultural land."Land" footprint shows the average value of removal of main nutrients (NPK) and mineralization of humus during the formation of a crop from a conditional 1 ha.
Due to economic, social, and environmental reasons, Ukraine must take urgent measures to develop a consistent policy for assessing and reducing its land footprint.This includes standardizing land use methodology and creating the necessary database for its accounting, auditing, and assessment through digitalization and GIS technologies.Ukraine should also consider using water and carbon land footprints in assessments of their impact on natural resource management (in the context of European integration and land footprint standardization methodologies in the EU).Implementing ISO 28,000 series standards for logistics (including water, land, material, and carbon footprints) and developing a new food policy aimed at reducing the use of all types of resources is essential.
Reduce the import of virtual land, which incurs real financial costs (ecological-economic calculations are not used or are not comprehensive).It is crucial to justify the scales of existing and socio-ecologicaleconomically reasonable land use.The exclusive focus of producers on the profitability of crop cultivation over the past decade in the Rivne Oblast has led to a 10-fold increase in soybean cultivation area, a 5-fold increase in corn, and a 22-fold increase in sunflower cultivation.As a result, in 2020, nitrogen yield increased by 34%, phosphorus by 86% compared to 1990, while potassium yield decreased by 40%.The level of humus mineralization has been steadily increasing since the early 2000s and currently averages 1.42 t/ha, which is 13% higher than in the 1990s and 22% higher than in the 2000s.This indicates increased pressure on the region's soils.
The government of the country should be obliged to implement state policy to reduce its (primarily land and water) footprints.Both the government and businesses should focus on: reformulating food production (production of finished products rather than raw material exports), greening agribusiness and diversifying it, reducing the ecological footprint and energy consumption through increased energy efficiency, adapting marketing and advertising strategies for local and niche productions, and using ecofriendly packaging, among other measures.

Figure 1 .Figure 2 .
Figure1.Dynamics of the structure of cultivated areas in Rivne Oblast (excluding private households).Source: formed by the authors based on[43]

Figure 4 .
Figure 4. Yield of essential nutrients by crops per hectare.Source: compiled and calculated by the authors based on [43, 45].

Figure 5 .
Figure 5. Yield of essential nutrients by crops in Kostopil district per hectare (Polissia zone).Source: compiled and calculated by the authors based on[43,45].

Figure 6 .
Figure 6.Yield of essential nutrients by crops in Radiviliv district per hectare (Forest-Steppe zone).Source: compiled and calculated by the authors based on[43,45].
1 ∑ Dynamics of soybean cultivation area in Rivne Oblast.Source: formed by the authors based on