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Productive windbreaks for environmental management of agricultural land: spatial targeting, comparative techno-economic assessment, and risk analysis of a European hazel (Corylus avellana L.) system

This study integrates spatial analysis with techno-economic modeling to demonstrate that while a significant portion of arable land in northeastern Slovenia lacks nearby woody vegetation, implementing productive European hazel windbreaks offers a financially viable investment with a strong return, provided that yield uncertainties are managed.

Original authors: Karmen Pažek¹, Alen Bolkovič¹, Tina Lešnik¹, Damjan Jerič², Črtomir Rozman¹

Published 2026-09-01

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CC BY 4.0

Original authors: Karmen Pažek¹, Alen Bolkovič¹, Tina Lešnik¹, Damjan Jerič², Črtomir Rozman¹

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Wind is a powerful force that shapes the land, but when it blows unchecked across open fields, it can strip away the very soil that farmers rely on to grow food. This process, known as wind erosion, not only depletes the earth's fertility but also creates dust clouds that can damage young crops and reduce air quality. For decades, the solution has often been to plant rows of trees and shrubs, known as windbreaks, to act as living barriers that slow the wind and hold the soil in place. However, planting these trees is a significant investment for a farmer. It requires money for saplings and labor, and it takes up land that could otherwise be used for immediate crops. The challenge has always been finding the right balance: determining exactly where these barriers are needed most, and figuring out if planting trees that also produce something valuable, like fruit or nuts, can make the financial risk worth taking for the individual farmer.

In northeastern Slovenia, a team of researchers set out to solve this puzzle by combining a map-based search for vulnerable land with a detailed look at the economics of three different types of windbreaks. They began by looking at the landscape to see where the land was most exposed. Using digital maps of forests, hedges, and tree lines, they measured the distance between these natural barriers and the open fields. They found that nearly half of the arable land in the region—about 45 percent—was located more than 200 meters away from any existing woody vegetation. This meant that vast, continuous stretches of farmland were essentially unprotected, creating a clear need for new barriers. The largest of these open areas were concentrated in the lowland plains, where some single blocks of farmland stretched over 1,000 hectares without a single tree or hedge nearby.

Once they identified where the windbreaks were needed, the researchers asked a second, more difficult question: could a farmer afford to plant them? To answer this, they modeled three different designs on a one-hectare plot of land. The first design was a traditional, non-productive belt made of various native trees and shrubs, planted solely for protection. The second design added some berry-producing bushes to the mix, hoping to generate a little extra income. The third design was the most ambitious: a productive system featuring European hazel trees for their nuts, supported by a row of tall poplar trees to provide height and protection.

The results showed a clear difference in financial potential. The traditional, non-productive belt cost money to maintain every year with no direct income to offset those costs. The design with berry bushes came close to breaking even but still resulted in a small annual loss. The hazel and poplar system, however, told a different story. While it required the highest initial investment—costing over 22,000 euros to establish and reach full production—it eventually generated significant revenue. At full maturity, the model predicted the hazel trees would produce about 2,080 kilograms of nuts per hectare. If sold at a moderate price, this single hectare could generate a profit of nearly 10,000 euros per year once the trees were fully bearing fruit.

The researchers were careful to ensure their numbers were accurate, particularly regarding when costs were counted. They discovered that if you simply added up all the early costs and then counted them again in the yearly budget, the math would look much worse than it actually was. When they corrected this by spreading the costs over the years they actually occurred, the financial picture improved dramatically. Their calculations showed that an investor could expect to get their money back in the eleventh year, and over a thirty-year period, the project would yield a strong return.

However, the study also highlighted that this success depends heavily on the trees actually producing the expected amount of nuts. The researchers ran thousands of computer simulations to test how sensitive the project was to changes in yield, price, and cost. They found that the amount of hazelnuts produced was the single most important factor. If the trees produced significantly less than expected, the financial benefits could disappear. The price of the nuts also mattered, but not as much as the harvest size. This suggests that while the idea of a productive windbreak is financially sound, it is not a guaranteed win; it relies on the trees thriving and the farmer successfully harvesting and selling the crop.

The study concludes that the best approach is a two-step process. First, use maps to find the large, open fields that are most in need of protection. Second, before planting, farmers and advisors must look closely at the local conditions to see if a productive system like hazel is viable. The research shows that turning a windbreak into a source of income can make the investment attractive to farmers, but it requires careful planning and realistic expectations about the harvest. The work does not prove that these specific trees will work perfectly in every field, as the models were based on calculations rather than long-term field measurements, but it provides a clear roadmap for where and how these systems could be introduced to protect the land while supporting the farm's economy.

Technical Summary: Productive Windbreaks for Environmental Management of Agricultural Land

Problem Statement
Wind erosion poses significant risks to soil fertility and crop stability in intensively cultivated European landscapes, yet the adoption of windbreaks is often hindered by the lack of clear spatial targeting and the financial unviability of non-productive woody structures for private farmers. While windbreaks offer environmental benefits such as erosion control and biodiversity support, their establishment is a private investment decision where costs (planting, maintenance, land opportunity) often outweigh immediate returns unless marketable outputs or public payments are included. The study addresses the dual challenge of identifying where additional woody structures are most needed in northeastern Slovenia and determining whether a productive windbreak design (specifically European hazel) can be financially viable for farmers under realistic investment conditions.

Methodology
The research employs an integrated spatial and techno-economic case study framework focused on northeastern Slovenia (Podravska and Pomurska regions).

Spatial Targeting: Using ArcGIS Pro, the study analyzed the proximity of 100,970.81 ha of arable land to existing woody vegetation (forests, hedgerows, and tree lines). Distance buffers (0–50 m, 50–100 m, 100–200 m) were generated to identify structurally open agricultural complexes located more than 200 m from any mapped woody feature.
Techno-Economic Scenarios: Three 1-hectare windbreak designs were modeled:
1. Scenario 1: A non-productive multi-row tree belt (oak, lime, cherry, hornbeam, maple).
2. Scenario 2: A multi-row belt incorporating productive shrubs (elderberry and dog rose) with yields restricted to 20% of conventional plantation estimates.
3. Scenario 3: A productive design featuring European hazel (Corylus avellana L.) in outer rows and Lombardy poplar (Populus nigra L. 'Italica') in the center, with a density of 416 hazels and 416 poplars per hectare.
Financial Modeling: The study utilized a 30-year investment horizon with a 5.5% discount rate. A critical methodological contribution was the "temporal harmonization" of cash flows. The authors identified and corrected a common error where cumulative pre-bearing costs were aggregated at $t=0$ while simultaneously retaining annual maintenance costs in subsequent years, leading to double-counting. The harmonized model separated initial establishment costs from annual maintenance to ensure consistent cash flow sequencing.
Uncertainty Analysis: Robustness was assessed through one-factor sensitivity analysis, break-even analysis, and a conditional Monte Carlo simulation (10,000 iterations) using beta-PERT and triangular distributions for yield, price, and costs. Farm-level integration was demonstrated using the "Farm Manager" decision-support system.

Key Results

Spatial Findings: Approximately 45.83% of the arable land in the study area is located more than 200 m from both forests and hedgerows/tree lines. The ten largest structurally open arable complexes range from 493 to 1,171 ha, concentrated in the Drava-Ptuj and Mura lowlands.
Economic Comparison:
- Scenario 1 (Non-productive): Generated no direct revenue, resulting in an annual private deficit of ~EUR 709.
- Scenario 2 (Shrubs): Generated EUR 4,795 in revenue but incurred EUR 4,995 in costs, resulting in a slight annual deficit of EUR 199.
- Scenario 3 (Hazel): At full bearing (Year 7+), with a yield of 2,080 kg ha⁻¹ and a production budget price of EUR 6 kg⁻¹, the design generated a production financial result of EUR 9,763.73.
Investment Viability (Scenario 3): After temporal harmonization (removing double-counted costs), the 30-year investment model using a conservative price of EUR 4 kg⁻¹ yielded a Net Present Value (NPV) of EUR 41,997, an Internal Rate of Return (IRR) of 14.82%, and a discounted payback period of 11 years.
Uncertainty and Sensitivity: Monte Carlo analysis identified yield as the dominant source of uncertainty (Spearman correlation $\rho = 0.901$ ), followed by selling price ( $\rho = 0.385$ ). The probability of a positive NPV was 97.28% with an archived budget payment and 91.62% without it. The break-even yield at EUR 4 kg⁻¹ was 1,020.8 kg ha⁻¹.

Significance and Claims
The paper claims that combining spatial screening with rigorous, temporally consistent economic assessment allows for the identification of candidate areas and investment conditions for productive windbreaks. Key contributions include:

Spatial Prioritization: The study demonstrates that nearly half of the arable land in the region lacks proximity to existing woody structures, providing a data-driven basis for prioritizing field-level wind-risk diagnoses in specific lowland complexes.
Economic Viability of Productive Systems: The results suggest that including a marketable output (hazelnuts) can significantly improve the private financial result of windbreak establishment compared to non-productive belts, potentially overcoming the financial barrier to adoption.
Methodological Rigor: The paper emphasizes that accurate investment appraisal in agroforestry requires the explicit separation of initial capital outlays from pre-bearing maintenance costs to avoid double-counting, which can materially distort NPV and IRR calculations.
Decision Support: The study illustrates how break-even analysis and uncertainty modeling can inform policy and advisory services, distinguishing between scenarios where private investment is sufficient and those where targeted public support (e.g., for risk reduction or ecosystem services) is necessary.

The authors explicitly state that these findings are case-study statements based on modeled outcomes and do not constitute statistical hypotheses about the broader population of Slovenian farms. They further note that the study does not estimate causal biophysical effectiveness (e.g., wind speed reduction or soil erosion rates) due to the lack of field control plots, asserting that field validation remains necessary before inferring biophysical performance.

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