Agriculture that appears to be more eco-friendly but uses more land may actually have greater environmental costs per unit of food than “high-yield” intensive farming that uses less land, a new study has found.
The new findings by Cambridge scientists suggest that more intensive agriculture is the “least bad” option for feeding the world while saving species provided use of such “land-efficient” systems prevents further conversion of wilderness to farmland.
Researchers suggest intensive farming could meet rising food demand in a limited area and allow more natural habitats than other lower yielding systems.
Intensive farming techniques have been criticised for creating pollution, water scarcity and soil erosion. However, the study published earlier this month in the journal Nature Sustainability shows this is not necessarily the case.
How the study worked
Scientists compared the environmental costs of producing a given amount of food in different ways – such as greenhouse gas emission, fertiliser and water use.
Previous research compared these costs by land area. As high-yield farming needs less land to produce the same quantity of food, the study’s authors say this approach overestimates its environmental impact.
Their results from four major agricultural sectors suggest that, contrary to many people's perceptions, more intensive agriculture that uses less land may also produce fewer pollutants, cause less soil loss and consume less water.
However, the team behind the study, led by scientists from the University of Cambridge, caution that if higher yields are simply used to increase profit or lower prices, they will only accelerate the extinction crisis we are already seeing.
“Agriculture is the most significant cause of biodiversity loss on the planet,” said study lead author Andrew Balmford, Professor of Conservation Science from Cambridge’s Department of Zoology. “Habitats are continuing to be cleared to make way for farmland, leaving ever less space for wildlife.
Our results suggest that high-yield farming could be harnessed to meet the growing demand for food without destroying more of the natural world.
"However, if we are to avert mass extinction it is vital that land-efficient agriculture is linked to more wilderness being spared the plough.”
The Cambridge scientists conducted the study with a research team from 17 organisations across the UK and around the globe - including Poland, Brazil, Australia, Mexico and Colombia.
The study analysed information from hundreds of investigations into four vast food sectors, accounting for large percentages of the global output for each product:
- Asian paddy rice (90%);
- European wheat (33%);
- Latin American beef (23%); and
- European dairy (53%).
Examples of high-yield strategies include enhanced pasture systems and livestock breeds in beef production, use of chemical fertilizer on crops, and keeping dairy cows indoors longer.
In field trials, inorganic nitrogen was found to boost yields with little to no greenhouse gas “penalty” and lower water use per tonne of rice.
Per tonne of beef, the team found greenhouse gas emissions could be halved in some systems where yields are boosted by adding trees to provide shade and forage for cattle.
The study only looked at organic farming in the European dairy sector but found that – for the same amount of milk – organic systems caused at least one third more soil loss, and take up twice as much land, as conventional dairy farming.
Co-author Prof. Phil Garnsworthy from the University of Nottingham, who led the dairy team, said: “Across all dairy systems we find that higher milk yield per unit of land generally leads to greater biological and economic efficiency of production.
"Dairy farmers should welcome the news that more efficient systems have a lower environmental impact.”
Conservation expert and co-author Dr. David Edwards, from the University of Sheffield, said: “Organic systems are often considered to be far more environmentally friendly than conventional farming, but our work suggested the opposite. By using more land to produce the same yield, organic may ultimately accrue larger environmental costs.”