A TREE. In agricultural production, crops get the lion’s share of attention – and for good reason – but one particular aspect of this delicate system is disappearing from view.
Since a number of decisive initiatives to plant shelterbelts on the Prairies in the 1930s to keep topsoil from taking to the air, these long stretches of trees and shrubs on agricultural lands have been unravelling like a loose thread on a well-loved quilt.
But other than a stirring sense of dismay some people may feel at the loss of trees on the agricultural landscape, what may be disappearing along with it?
THE BENEFITS of shelterbelts to help retain soil, catch snow for spring moisture and protect crops from strong winds are relatively well known.
But though you may not see it among the shady branches and iridescent leaves as you drive by, shelterbelts also provide respite for a variety of beneficial insects that often provide a valuable service to growers.
“Every living thing on Earth needs a couple of things: food, shelter, a habitat, a place to live,” says says Shathi Akhter, agro-ecosystems research scientist with Agriculture and Agri-Food Canada. “Shelterbelts serve as a habitat for many beneficial species that are important to crops.”
Akhter says that with nearly 400 species of bees in the Prairie region, shelterbelts provide a habitat for not only them, but predator insects such as parasitic wasps that not only assist in pollination, but prey on crop pests. Other beneficial insects, such as a wide range of spiders and carabids, have also found flavour with insects that threaten crops.
During a discussion at Manitoba Ag Days in 2020, retaining natural areas for beneficial insects was a strategy also promoted by Alejandro Costamagna, a professor of entomology at the University of Manitoba.
“Keeping some natural areas that are not sprayed, that are permanent habitats… it’s a good idea,” said Costamagna. “We need to give more value to natural enemies and recognize that sometimes we don’t see them. Look for them, they are there and they are doing an important pest control service for growers.”
THE DUST Bowl Days of the 1930s saw immense dust storms lift hundreds of millions of tonnes of dirt into the air and crops failed. It was during this period that a swift decision to plant shelterbelts became part of a strategy to help keep topsoil grounded.
According to the U.S. Department of Agriculture, it takes a bare minimum of 100 years – depending on the area – to create one centimetre of topsoil. So to say it’s essential that growers do what they can to keep topsoil in place is an understatement.
“We’re losing our shelterbelts at an alarming rate,” says Melanie Dubois, senior riparian and biodiversity biologist with Agriculture and Agri-Food Canada. “Land prices are really high, there’s not a lot of land available and machinery is getting bigger. That puts pressure on those more natural areas that were perhaps left in the past.”
Pressure indeed. In 2019, Shathi Akhter estimated that about 60,000 kms of shelterbelt remained in Saskatchewan, and that they are disappearing across the Prairie provinces at a rate of about 600 kms per year. That’s roughly the distance between Winnipeg and Regina, or if you started walking and counted off about 825,000 steps.
But concern about soil going adrift isn’t the only issue. It’s also what we can’t see with the naked eye that can get swept up along with it.
Research on agroforestry practices is gaining ground as agricultural sustainability and improving soil health gains more focus. A research paper published in 2018, Agroforestry for soil health by Jeanne Dollinger and Shibu Jose, that included research from 28 studies worldwide, concluded there is solid evidence that the integration of trees and agriculture increased soil organic carbon, improved both soil nutrient availability and soil fertility, and enhanced soil microbial activity that improved soil health.
In 2019, Akhter presented data from a multi-year project she’s conducting that looks to discover if soil microbe concentrations can make nutrients more available to crops. Preliminary results of the study look promising as concentrations of soil microbes where native habitat and shelterbelts were higher when compared to open field.
And as shelterbelts disappear, their ability to help contribute in the fight against one of humanity’s greatest threats is also lessened.
THE PACE of climate change and record-breaking temperature increases across the globe in recent years are of increasing concern. The accumulation of greenhouse gases in our atmosphere – particularly carbon dioxide (CO2) – is the main contributor.
According to the National Oceanic and Atmospheric Administration, the 10 warmest years on record have all occurred since 2005.
Climate change is poised to subject farmers to new extremes, and while benefits such as a longer frost-free season and an increase in growing degree days may benefit crop yields, Natural Resources Canada warns that, “An increase in climate variability and the frequency of extreme events would adversely affect the agricultural industry. A single extreme event (later frost, extended drought, excess rainfall during harvest period) can eliminate any benefits from improved ‘average’ conditions.”
By their nature, trees are literally designed to help mitigate the challenge of climate change. The Arbour Foundation estimates that a single mature tree removes approximately 21.7 kg of CO2 from the air each year.
In 2019, Akhter estimated that existing shelterbelts for the six most common shelterbelt species in Saskatchewan have sequestered nearly 11 Tg (teragram) of carbon, worth as much as $600-million dollars at $15/tonne of carbon.
Akhter plans to conclude a project in 2021 that aims to expand the knowledge of how shelterbelts on farmland can mitigate greenhouse gas emissions. Key to the plan will be creating more awareness among farmers to the carbon capture potential of shelterbelts.
In order to seed our future, it is essential that we safeguard the investments made in decades past that have helped our food grow in a diverse and thriving environment.
By not protecting and recognizing the contributions that shelterbelts provide to agricultural production, this living vault that is a home for biodiversity, keeps topsoil grounded, and can help in the fight against climate change, will be difficult to replace due to the amount of time it would take to rebuild .
Contributor: Greg Berg