In many parts of the world, fields are filled with grazing animals—but few trees or crops. Now a different approach—silvopasture or the intentional practice of combining trees, livestock, and forage plants on the same land—is growing in popularity due to its many benefits for people, animals, plants, and the environment.
In Brazil, a country battling deforestation in its Amazon basin and other parts of its land, some farmers are exploring ways to increase silvopasturing.
Deforestation Imperils Land and Air
Forests around the world are under threat from rising deforestation and the local and global effects of climate change. Indeed, agricultural expansion is the cause of 80% of deforestation in the global tropics and sub-tropics.
In Brazil, cattle-ranching is one of the leading drivers of deforestation. Ranchers clear away forests, releasing vast amounts of greenhouse gas into the atmosphere. If they use unmanaged cattle ranching, in which animals roam free, their herds soon tarnish the land, leaving it less productive, damaging soils and eventually leaving little to no vegetation—meaning less carbon is absorbed by the land. Ranchers move on to new ground, and the cycle continues.
Silvopasture could help to alleviate some of these problems.
It’s estimated that around 1.36 billion acres of land are currently under silvopasture worldwide, with successful large-scale projects in places spread as far as Japan and Portugal. While the amount of silvopasture land in Brazil has been rising, widespread adoption of this practice still faces several challenges.
Silvopasture and Healthy Landscapes
Silvopasture is created either by planting trees on existing pasture, or only removing certain areas of woodland when preparing land for grazing or agriculture. When a silvopasture site is brought into balance, there should be a healthy growth of grassland that feeds the animals and helps recycle nutrients into the land for crops.
One of the major benefits of the system is improved animal health. By including trees into the landscape, cattle have access to shelter and shade, and more space to graze. This reduces the stress of the animals, and allows them to spend less of their energy on temperature maintenance and more on growth—research suggests it can increase animal weight by up to 10%. This results in improved lifestyle for the animals, and healthier profits for the ranchers.
In the United States, many farmers are introducing silvopasturing systems on their land. On Early Boots Farm in Minnesota, farmer Tyler Carlson took up silvopasturing in 2012. He now sees many benefits to the system, notably the expanded grazing area for his livestock. Carlson thinned out several acres of dense forests, where previously no forage grew underneath. Now the silvopasture grasslands compete with open grasslands and are even more productive in times of extreme heat and drought.
The introduction of native tree species also adds a range of ecological benefits to an agricultural landscape, boosting local wildlife and biodiversity by offering new habitats and sources of food. Strengthening biodiversity improves a landscape’s resilience to adverse weather events, including those brought on by climate change. The plant life also helps the spread of fungi that are essential to healthy soil function.
Financial and Climatic Benefits
Silvopasture also brings a range of economic incentives for farmers aside from healthier animals. Economic analyses have shown that these systems can be more profitable than forestry or simple grazing.
In traditional silvopasture systems, the trees are productive: Their fruits or nuts can be exported to generate profit; other trees can be sustainably harvested for their timber.
Trees also mitigate flood damage by opening up soils with their roots and allowing water to seep in. In the face of increasing weather events over the next century, this could prevent huge losses from flooded agricultural land.
Estimates suggest a pasture with trees can sequester up to ten times more carbon dioxide from the atmosphere than treeless land.
Adding more trees into the landscape—or removing fewer—has clear positive effects on both local and global environments. Estimates suggest a pasture with trees can sequester up to ten times more carbon dioxide from the atmosphere than treeless land.
Through a process known as evapotranspiration, intact forests also soak up water from the ground and emit it as water vapor, which evaporates and cools the surrounding environment.
Conversely, removing trees breaks this cycle. One recent study found that deforestation can boost temperatures in local areas, on top of the rising temperatures due to global climate breakdown. On the flip side, another study found that adding trees into pasture could lower local temperatures (by up to 2.4°C = 4.32°F).
Researchers in Brazil and around the world are studying silvopasture to understand and quantify the benefits it can bring. In one study, carried out at the University of New Hampshire, scientists compared plots of silvopasture, regular pasture, and forest. They removed 50% to 60% of trees from silvopasture plots, then seeded foraging plants before introducing cows. Then, they set up meteorological stations to measure microclimatic variables in the air and soil. They found silvopasture plots emitted less carbon dioxide and nitrous oxide into the atmosphere from the soil, while carbon storage stayed the same.
“Our results suggest that silvopasture may offer a biogeochemical ‘middle ground’ between intact secondary forests and managed open fields, retaining the climate benefits of forests while enabling expansion of the agricultural land base,” the researchers write.
Silvopasture in Brazil
In Brazil, agroforestry has been practiced by indigenous communities for thousands of years. In the Amazon, the combination of forestry and crop-growing has long been used to produce cacao, açai, coffee, and nuts. Silvopasture is growing in popularity in both the Cerrado, a tropical woodland savanna, and the Gran Chaco, a forest region over twice the size of California that spreads over Brazil, Bolivia, Paraguay, and Argentina.
A recent study reviewed the scientific impacts of silvopasture in the Caatinga, a dryland ecosystem in Brazil’s northeast home to around twenty-five million people. As far back as the 1860s, residents realized the negative impact of livestock on the local biome and started growing trees in pasture to improve livestock productivity. There are now many books and reports describing best practices.
As far back as the 1860s, residents realized the negative impact of livestock on the local biome and started growing trees in pasture to improve livestock productivity.
Most of the Caatinga dryland is located in a climatic depression, which blocks rainfall from reaching the area. Rainfall varies hugely between years, and every few decades, the region faces a severe drought lasting as long as five years.
A team of scientists from the University of Florida found that maintaining 40% tree cover would produce a sustainable silvopastoral system in this region to help alleviate some of the climate issues. The results could benefit similar drylands, 90% of which exists in developing countries.
Another two-year study examined cattle growth in legume silvopasture plots compared to grass monoculture. The researchers investigated the impact of the introduction of two tree legumes—gliricidia and mimosa—into a landscape in the sub-tropical state of Pernambuco. They found that the introduction of gliricidia increased animal productivity more than the monoculture or mimosa, indicating that the type of legume introduced is key to success. Silvopasture systems including tree legumes could therefore provide numerous ecosystem services and reduce the carbon footprint in livestock systems in the tropics.
In Brazil, this new growth could help to regenerate deserted land, restoring nutrients to the soil.
Challenges
Of course, there are barriers to the adoption of silvopasturing in Brazil.
Ultimately, whether silvopasture or similar agroforestry projects can have any tangible impact depends on the political discourse within the country. The Amazon rainforest will remain under tremendous threat from deforestation and forest fires unless long-term environmental protections are implemented across all administrations.
Cost is also an issue. To establish effective silvopasture requires high up-front costs, and long-term maintenance fees. Each element of silvopasture comes with its own associated needs and costs.
Another potential hurdle is culture. Owning cattle offers a level of respect within certain parts of Brazilian society, meaning some ranchers could be averse to changing their ways. However, according to the research of Rachael Garrett at Boston University, this could also help to spread the idea.
Garret visited a Brazilian silvopasture farm in 2017. The cattle rancher had swapped his cattle from those raised for beef to dairy cows; he had planted rows of eucalyptus trees to shade the cows and provide an additional income source, and regularly rotates his crops to renew the soil.
The amount of integrated agroforestry land in the Brazil jumped more than seven-fold between 2010 and 2016, reaching 11.5 million hectares.
Her research suggests that if higher-status members of society successfully run silvopasture farms like this, others could follow. “Status counts. Somebody needs to prove that it works,” she said in a statement.
And it could be working: data from Embrapa, the Brazilian Agricultural Research Corporation, suggests the amount of integrated agroforestry land in the country jumped more than seven-fold between 2010 and 2016, reaching 11.5 million hectares (44,401 square miles).
Farmers across Brazil are showing increased interest in silvopasture. In Pará, for example, farmers are experimenting with planting commercially important trees such as eucalyptus and African mahogany.
If Brazilians can find the political and financial will to promote silvopasture across the country, it would be a win-win for Brazil and the global climate.
*Richard Kemeny writes about archaeology, marine biology, oceanography, ecology, technology, and the environment.
Kommentare