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Why Agroforestry?

Photo taken by AGFORWARD project, alley-cropping in Forst, Northeastern Germany

Why agroforestry?

Agroforestry improves the health of the agroecosystems (agricultural ecosystems) by incorporating more trees into the land and mimicking natural ecosystems. A healthier agroecosystem leads to a wide range of benefits for the farmer, the environment and the society as a whole. 

These benefits can be broken down into:

  1. Increased farm resiliency and productivity 

  2. More diverse and profitable farm-enterprises

  3. Societal benefits: for the farmers and the society 

  4. Environmental benefits

*Below I am marking in bold the main benefits linked to agroforestry that are specifically relevant for farmers. 

 

1. Increased farm productivity and resiliency 

There is enough evidence showing that temperate agroforestry systems produce more per hectare compared to if the crops, animals or trees would be cultivated separately (monoculture systems). This concept is known as the land-equivalent-ratio (LER), which means how much more can a land produce by intercropping rather than by sole-cropping. The image below shows an example of an agroforestry system with a LER of 1.4, which means that 100 hectares of agroforestry produces as much crop and tree products as 140 hectares of farmland where trees and crops are separated.

Land Equivalent Ratio (Mead and Willey, 1980)

Source: Land Equivalent Ratio (Mead and Willey, 1980) The Concept of Land Equivalent Ratio and Advantages in Yields from Intercropping [1].

 

A pan-European project analyzed 42 combinations of trees and crops in silvoarable agroforestry, and modelled LERs of at worst 1.0 (equal to monoculture) and at best 1.4 (40% more productive) [2]. Most LERs were in the range of 1.2-1.3, meaning that European agroforestry systems were on average 20-30% more productive than monoculture farming systems. 


Land Equivalent Ratio (LER) for different tree species in silvoarable agroforestry 

Land Equivalent Ratio (LER) for different tree species in silvoarable agroforestry

Source: Graves, A.R. et. al. (2007) Development and application of bio-economic modelling to compare silvoarable, arable and forestry systems in three European countries, Figure 4 [3].

Well designed agroforestry systems integrate trees into farms in a way where the synergistic relationships between the trees, the crops and the animals are maximized. Trees provide shelter and wind protection, while at the same time reducing soil erosion and nutrient loss. Additionally, trees grow better in agroforestry systems compared to orchards or forestry, because they have more space between each other leading to less root and canopy competition. These synergistic relationships lead to a more balanced, resilient and productive system that can better cope with the ever-increasing environmental changes.

2. More diverse and profitable farm-enterprises

Working with agroforestry is like investing in a farm´s infrastructure and investing in a new farm-enterprise at the same time. 

The farm´s infrastructure represents all the agroecological benefits that trees provide, such as less soil erosion, less nutrient loss, more water retention, more biodiversity, and more protection from the wind. These benefits improve the living conditions of the crops and animals in the farm, which in turn increases their yields and resiliency. 

Farmers are also investing in new enterprises when working with agroforestry, because they are producing new products from their trees. Additionally, farmers can minimize the costs in their farms by being less dependent on external inputs and utilizing the tree-products on their farms.

The most common tree-products that farmers produce in agroforestry are the following:

  1. Food for humans (berries, fruits, nuts, etc.)

  2. Fodder for animals

  3. Material: fiber, timber, energy

Agroecological orchard near Valencia, Spain

Vicente Borras examining the quality of the peaches from his agroecological orchard near Valencia, Spain. Vicente produces 18 different fruit varieties in the 17 hectares of his farm. He has 165 different species of trees and shrubs in the hedges surrounding his orchards. Source: U-garden project

3. Social benefits: for the farmers and the society 

At the end of the day, why we do anything in life is due to the emotions that we want to feel. Many people find joy and meaning when helping the environment and the society as a whole. For many farmers, creating a healthy agroecosystem feels more compelling than just managing a farm. Additionally, integrating more trees in agriculture creates more aesthetically appealing workplaces. 

Agroforestry systems can foster more social connections in the farms, either by attracting visitors and tourists to the farm, including friends or family members in the tree management, or by employing new people on the farm.  

A rural land that is more interconnected, ecologically stable, and aesthetically appealing improves the livelihood of the people living in that region. More beautiful landscapes also attract more visitors, which is better for the local tourist industry. Finally, it is worth pointing out that a healthy ecological system brings a wide range of health, psychological and monetary benefits to a society that is hard to quantify. 

 

4. Environmental benefits

The scientific evidence is clear: agroforestry stands out as one of the agricultural practices with the highest potential to generate multiple environmental benefits. 

One seminal scientific investigation that demonstrates this has been performed by the Joint Research Center of the European Commission. The European Commision wanted to gather all possible scientific evidence to determine which agricultural practices could help Europe meet their environmental goals in the new CAP 2022-2027 (Common Agricultural Policy). In order to do this they analyzed 32 meta-analyses, 29 of which compared agroforestry versus conventional agriculture. Each meta-analysis summarized the results from 3 - 140 studies. The meta-analyses consistently showed that, compared to conventional agriculture, agroforestry performs better in the following areas

(1) reducing erosion

(2) improving biodiversity and increasing the number of pollinators

(3) reducing diseases and pests in agriculture

(4) increasing carbon sequestration in the soil

(5) reducing greenhouse gas emissions

(6) increasing soil water retention capacity

Below, I explain in more detail how agroforestry contributes to each of these areas. I am highlighting the most important findings of the cited study by underlining them in the following texts. 

Soil health:

The health of the soils reflects the health of the agroecosystem. A healthy soil allows farmers to produce better yields in the long run. Unfortunately, the health of agricultural soils is deteriorating around the world. One of the main factors affecting soil health is soil erosion and nutrient loss. Globally, conventional cropland erodes at a rate of 30 tons per hectare per year [4]. Comparably, erosion rates in a forest range from .004 to .05 tons per hectare per year [5]. Overall, soil is being lost from agricultural areas 10 to 40 times faster than the rate of soil formation [5]. This results in trillions of dollars in lost yields and livelihoods, putting humanity´s food security at risk.

Happy worm and soil health

Agroforestry reduces soil erosion, while at the same time making the soils more fertile due to an improved nutrient-cycling, increased soil organic matter, increased soil carbon and higher water retention due to less evapotranspiration.

 

Four meta-analyses demonstrated that, compared to conventional agriculture, agroforestry increased nutrients stocks in soils by 20-70% [6]. Moreover, 3 meta-analyses showed that agroforestry decreases soil erosion and nutrient runoff by 50-80% [6].

 

Biodiversity and pollination: 

Tree based ecosystems are the richest land-based ecosystems on the planet. Globally, forests cover almost one third of the land area, and they hold around 80% of all land-based biodiversity [7]. Integrating trees into farms creates new habitats for insects, birds and other animals. This increase in biodiversity creates more stable and resilient systems that can better cope with environmental changes, pests and diseases. Trees and shrubs also feed the pollinators, which improves farmers yields by pollinating the plants that feed us.

Bee pollinating

Three different meta-analyses demonstrated that, compared to conventional agriculture, agroforestry increases biodiversity indexes by 20-50% (covering several taxa like plants, birds, invertebrates, reptiles, fungi, mammals, and amphibians or functions (e.g. pollination)) [6].

 

Carbon sequestration:

Agroforestry can be a great tool to reduce the emissions of greenhouse gasses in agriculture. A shift from conventional agriculture to agroforestry can mitigate 14 - 27 tons of CO2* per hectare per year, at least for the first 14 years after establishment [8].

A study analyzing the carbon sequestration potential of various agricultural practices revealed that if all European farmers were to adopt agroforestry practices, Europe could sequester one-third of its CO2 equivalent** emissions (CO2-e emissions in the EU in 2007). This study also concluded that, among various agricultural practices including (1) agroforestry, (2) introducing hedges, (3) low and no tillage, and (4) cover crops, agroforestry is the agricultural practice with the highest potential to store carbon, accounting for 90% of the total potential of all the measures studied! (9).

* Accounting for C- sequestration in biomass and soil and for changes in net emissions of soil-CH4 and N2O emissions.

 

**CO2 equivalent (CO2e) expresses the warming effect of greenhouse gasses in terms of the equivalent amount of carbon dioxide emitted. For example, over a 20 year period 1 ton methane (CH4) has a global warming potential equal to 81 tons of CO2, and 1 ton of nitrous oxide (N20) has a global warming potential equal to 273 tons of carbon dioxide [9].

 

The carbon sequestration potential of different agricultural measures in Europe

The carbon sequestration potential of different agricultural measures in Europe

Source: Aertsens J. et. al. (2012) Valuing the carbon sequestration potential for European agriculture, Table 1 [10].

Water:

Global warming, environmental pollution and the increased pressure on our natural resources is affecting the stability of water resources around the world. Given that freshwater is becoming a scarce and valuable resource, it will become increasingly important that we produce more food with less water and that we find ways to reduce water contamination. 

Integrating more trees in agricultural lands reduces evapotranspiration, improves the soil´s structure via the roots and increases the soil organic matter via the leaves. This leads to an increased water-holding capacity and improved water-infiltration. 

Cartoon drawing of a river

Additionally, agroforestry mitigates the environmental impact of common agricultural practices by reducing the amount of eroded particles that end up in streams, rivers and lakes (50-80% less soil erosion and nutrient runoff according to 3 meta-analyses) [6]. Less eroded particles in waterways means less sedimentation and less contamination from leached nutrients, fertilizers and pesticides.

According to 5 meta-analyses, the water retention in soils is increased to 50-100% when introducing agroforestry practices to conventional agriculture [6]. This is becoming increasingly important for farmers, due to the constant rise in temperatures and droughts.

Comment below on what you think about the topics discussed above? Do you have a different opinion? If you have implemented agroforestry in your farm, why did you do it? What were your reasons?

References:

[1] Land Equivalent Ratio (Mead and Willey, 1980) The Concept of Land Equivalent Ratio and Advantages in Yields from Intercropping

[2] Dupraz, C. et. Al. (2005) Synthesis of the Silvoarable Agroforestry For Europe project

[3] Graves, A.R. et. al. (2007) Development and application of bio-economic modelling to compare silvoarable, arable and forestry systems in three European countries, Figure 4

[4] Pimentel, D. et. al. (1995) Environmental and economic costs of soil erosion and conservation benefits

[5] Pimental D. et. al. (2013) Soil Erosion Threatens Food Production

[6] Schievano A. et. al. (2022) The benefits of Agroforestry for the environment, climate change mitigation and agricultural production – a global synthesis. EURAF 2022

[7] United Nations International Year of Forests, 2011

[8] Kim D. et. al.( 2016) Carbon sequestration and net emissions of CH4 and N2O under agroforestry: Synthesizing available data and suggestions for future studies

[9] IPCC (2021) 7.SM.6 Tables of greenhouse gas lifetimes, radiative efficiencies and metrics

[10] Aertsens J. et. al. (2012) Valuing the carbon sequestration potential for European agriculture

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