Why agroforestry is a promising climate change solution

PUBLISHED ON: MARCH 11, 2020 Source: https://www.renature.co/

Regenerative agroforestry provides a cross-cutting solution to many of the world’s challenges.

This is because integrating trees within agricultural systems includes not one but many benefits. Those include increased agricultural productivity, reduced hunger and poverty, women’s empowerment, biodiversity support, regenerated soils, enhanced farm resilience, improved and diversified diets, as well as: climate change mitigation. 

This article will focus on the latter: agroforestry as a solution to mitigate climate change. Indeed, agroforestry can take CO₂ out of the atmosphereand, thereby, counteract global warming.

Regenerative agroforestry also has great potential as a climate change adaptation solution – that means helping farmers and landowners to prepare for the impacts of climate change. For instance, agroforestry systems contribute to the health of the soil and increase biological diversity. These benefits increase farmers’ resilience and ability to cope with extreme weather events such as extreme rainfall or extreme drought. These weather extremes are becoming more common as a result of climate change.

This article will help you gain an in-depth understanding of how agroforestry can help mitigate climate change. A future article will discuss climate change adaptation in more detail. Want to stay up to date? Subscribe to our newsletter!

How agriculture is causing global warming

Currently, about 23% of the world’s total emission of human-made greenhouse gases (GHGs) comes from Agriculture, Forestry and Other Land Uses (AFOLU). Within AFOLU, most emissions come from deforestation and agricultural production.

Taking a closer look, emissions within AFOLU are roughly divided into two halves, the ‘FOLU-side’ of the equation (including emissions from forests and other land uses such as peatlands), and the ‘A-side’ of the equation (including emissions from agricultural activity). Each side accounts for about 50% of emissions.

Within agriculture, emissions arise from many different types of farming activities (figure 2). The top three contributors to emissions are enteric fermentation – livestock feed digestion from ruminants such as cows and sheep, manure on pasturelands, and the use of fossil-fuel-based chemicals (‘synthetic fertilizers’).

It is interesting to point out that, considering global trends in fertilizer use, synthetic fertilizer will likely become a larger source of emissions than manure on pasturelands. This demonstrates how agricultural emissions can be influenced by how we farm: in this case, using synthetic fertilizer versus not using synthetic fertilizer. 

We’ve now learned that temporary agriculture and deforestation are causing about a quarter of all human greenhouse gas emissions. We’ve also learned that agriculture contributes to emissions in many ways and that the type of management influences the total agricultural emissions.

How agriculture suffers the damages of climate change

Contemporary agriculture does not only drive climate change, but it is also affected by it. Global warming’s grave consequences can be seen within and beyond the agricultural community. For instance, global warming increases the frequency and intensity of extreme weather events, adversely impacts food security and terrestrial ecosystems, and is contributing to desertification and land degradation in many regions of the world.

Heatwaves, droughts, dust storms, desertification, heavy rainfall, changing rainfall patterns, flooding, and sea-level rise are some of the effects of climate change that currently impact humans and nature, and will continue to do so in the future.

Contemporary agriculture is both victim and driver of climate change

When we look at the bigger picture, it becomes clear that agriculture is causing its own demise. In a painfully ironic way, it is both accelerating climate change and suffering the damages of climate change at the same time. 

It should be noted that globally, there are differences in the extent to which regions cause agricultural emissions and to what level they are affected by it.

Let’s take two countries as an example: the United States and South Sudan.

In terms of agriculture as a cause of climate change, it is estimated that the agricultural sector in the United States emitted 0.38 billion tons of CO2 equivalents in 2016. As a comparison, South Sudan emitted only 0.05 billion tons of CO2 equivalents within the same year – a fraction of the emissions of the US.

In the US, the three largest emitters within the agricultural sector are 1) livestock feed digestion (enteric fermentation); 2) synthetic fertilizer; 3) manure management. In South Sudan the three largest emitters within the agricultural sector are 1) burning of the savanna; 2)  livestock feed digestion (enteric fermentation); 3) manure left on pasture.

These comparisons show how the emissions from the agricultural sector in both countries are skewed. The agricultural sector in the US emits much more than that in Sudan. Additionally, both countries’ agricultural emissions come from different practices. 

In terms of the damages, climate change is greatly damaging agriculture in both countries. Let’s take a closer look.

A grim outlook: California’s San Joaquin Valley

California is known as the breadbasket of the United States. California hosts the country’s most productive area in agricultural terms. Unfortunately, it is also one of the most “climate-challenged” regions of North America.

California’s agriculture is projected to experience lower crop yields due to extreme heat waves, heat stress and increased water needs of crops and livestock, as well as new and changing pest and disease threats. 

By 2060, expected yield decreases are 40 percent for avocado and up to 20 percent in oranges, grapes, walnuts, and almonds.

Many farmers are now switching to pistachios as they hope this nut will better tolerate future conditions under continued climate change. However, such changes are not big enough to fundamentally decrease the vulnerability of the industrialized agricultural system: “I see agriculture that is basically hydroponics. It’s like a person being fed/kept alive by an IV.” notes an agronomist from UN Davies.

South Sudan: Where climate change hits the hardest

In South Sudan – a country in which half of the population could be at risk of acute food insecurity in the near future – devastating rains and floods in several regions are projected to lead to ‘catastrophic’ food insecurityamong communities in which food security was already in a dire state.

We’ve seen that climate change is affecting countries worldwide. In the US, climate change is greatly threatening the country’s’ agricultural hotspot. In Sudan, climate change is devastating for food security, with a large number of people being highly vulnerable.

We’ve seen that today’s agriculture is contributing to climate change – causing it – as well as undermining the foundations of its own existence – and therefore suffering from it.

The necessity of redirecting agriculture onto a different course is unquestionable. Scaling of agricultural alternatives that mitigate climate change is urgently needed.

Agroforestry as a climate mitigation solution           

Instead of being a driver of climate change, agriculture can be turned into a solution. This solution is called Regenerative Agroforestry.

Regenerative Agroforestry has a high potential to mitigate climate change as it can remove significant amounts of GHGs from the atmosphere – making it a so-called “carbon sink”.

And, it does this – this being CO₂ sequestration – much better than conventional agriculture (figure 6). So, why is it that agroforestry is a climate change mitigation solution, whereas conventional agriculture is a climate change driver? Because of one magical element: trees!

Trees: Natural carbon pumps

Through photosynthesis, trees take CO₂ from the air and transform it into carbon that is stored in their trunk, branches, roots, and leaves. All this living tissue is referred to as the trees’ biomass.

Trees can store an impressive amount of carbon. For example, General Sherman (figure 7), the giant sequoia tree that is the largest known living tree on earth, is estimated to have sequestered about 1400 tons of CO₂ in its aboveground biomass: more than enough to compensate for the CO₂than the average American emits in a lifetime (and that is a lot)!

When a tree dies, part of the carbon from its biomass is stored in the soil. Through this process, organic matter in soils contains approximately three times more carbon than the atmosphere. However, care has to be taken that the carbon in the soil stays there. Why? Because soil can be a carbon ‘source’ or a carbon ‘sink’. This depends on the soil’s characteristics, the local climate, and – perhaps most importantly – the way the land is used, managed, and treated.

The process of successfully storing carbon in trees’ biomass and in the soil is referred to as carbon sequestration. 

Regenerative Agroforestry maximizes this pump

In Regenerative Agroforestry systems, management is actively focused on growing high amounts of biomass and returning as much of the dead biomass as possible to the soil. Both of these activities increase carbon sequestration. 

In addition, management in Regenerative Agroforestry systems attempts to minimize soil disturbance, mainly through avoiding tillage, to prevent the loss of carbon from the soil. By doing this, it is ensured that the soil remains a carbon sink and does not become a source. When soil remains undisturbed, stable carbon in the soil can remain there for hundreds to thousands of years. 

A great video that clearly demonstrates good management in a Regenerative Agroforestry system is Life In Syntropy.

Trees and climate change mitigation: a complex assessment

We now learned that trees in agroforestry systems can counteract climate change by storing carbon in their biomass and in the soil. But, how effective are they really – in other words – how much carbon do they actually store?

Calculating the potential of agroforestry systems in storing carbon is a complex issue. The type of tree, the type of soil, the climate, and natural resource management (including if animals and machinery are incorporated into the system) are all factors that decide exactly how much carbon is sequestered.

What’s more, not only carbon – in the form of carbon dioxide (CO₂) – but also other potent greenhouse gases, namely methane (CH₄) and nitrous oxide (N₂O), should be considered when calculating how much agroforestry systems contribute to mitigating climate change.

These gases should be considered because, over a period of 100 years, one unit of CH₄ and N₂O contribute 21 and 310 times more to global warming, respectively, than CO₂! Like CO₂, CH₄ and N₂O are gases that are naturally released as the soil life decomposes dead biomass. Management can influence the fluxes of these gases, for example through managing of manure and water in the soil (figure 9).

To obtain a comprehensible overview of the total mitigation potential of Regenerative Agroforestry, the total balance of the fluxes of these three greenhouse gases (CO₂, CH₄, N₂O) for all elements in the system is typically calculated and expressed in CO₂-equivalents. This way, they can all be compared to each other.

Agroforestry as a climate mitigation solution: emerging evidence

Despite this complexity, scientists are deepening their understanding of how much agroforestry can contribute to climate change mitigation. They do this by examining the information of all existing research that has been done on the topic so far. Comparing the results of many studies allows for more statistical certainty and understanding of effects. This approach taken by scientists is called a meta-analysis.

These meta-analyses provide valuable information. The general trend is clear: systems that incorporate more trees capture more carbon. One meta-analysis, using the information of more than 100 case studies, suggests that one hectare of a young agroforestry system annually takes 27 tons of CO₂ equivalents out of the atmosphere. This is balances out the emissions of 5 average world citizens.

When translating this to a global scale, estimates of the exact potential are harder to pinpoint and vary widely. The IPCC estimates that agroforestry has the mitigation potential of between 0.11 billion and 5.68 billion tons of CO₂ equivalents per year globally. This holds true under the estimate that agroforestry is applicable on 35% of the globally suitable lands (ice-free lands), mostly on rangelands and croplands.

When maintaining the estimated 27 tons of CO₂ equivalents per hectare per year, conversion to agroforestry could potentially mitigate 3.4 billion tons of CO₂-equivalents per year globally. This is more than India’s total annual emissions – the world’s 3^rd biggest emitter.

Estimating land availability

These calculations are based on the estimate that 126 million hectares of unproductive farmland worldwide can be successfully converted to agroforestry systems. However, some estimates of the amount of land that could potentially be regenerated are much larger.

For example, the World Resources Institute (WRI) estimates that worldwide, one and a half billion hectares are best-suited for ‘mosaic restoration’. This is a management approach for land in which forests and trees are combined with other land uses and where Regenerative Agroforestry can play a key role. Imagine the carbon sequestration potential then! 

The renowned Australian researcher and farmer Dr. Charles Massy takes another angle on the subject. In his astounding TED-talk he refers to the world’s leading resource for climate change solutions – Project Drawdown. The latter outlines currently available measures and their potential to either take CO₂ out of the atmosphere or prevent it from getting there.

Massy aggregated the potential of all solutions related to regenerative farming practices including various forms of agroforestry (11:50). Together, they embody the most potent climate change resolution whilst outperforming the ‘runner-up’ by far. To clarify what this means: Regenerative farming is a more effective climate measure than commonly promoted options such as onshore wind turbines or plant-rich diets.

Agroforestry’s climate benefits acknowledged by leading institutes

Given agroforestry’s potential as a climate mitigation solution, whilst simultaneously addressing other global issues, it is not surprising that renowned institutes endorse agroforestry as such.

Most notably, that is the Intergovernmental Panel on Climate Change – the IPCC. It also recognizes agroforestry as a low-cost solution for climate change adaptation, combating land degradation and desertification, and improving food security.

When compared to other land management approaches, as examined by the IPCC, the potential of agroforestry stands out: with mostly medium confidence, agroforestry has a highly positive impact on each of the five global issues (figure 12).