Global warning: agricultural production threatens life on Earth

James Cook University’s Professor Jeff Sayer is part of an international team that’s examining agricultural production in relation to nine ‘planetary boundaries’, which if breached could destabilise the Earth’s ecosystem.

“Agricultural production occupies 40 percent of the land surface of the Earth that isn’t covered by ice, and that’s expected to increase by another 8 percent by 2050, so it has a massive impact,” said Professor Sayer.

He said agriculture was already overwhelmingly responsible for breaching accepted biogeochemical limits – the flow of chemicals such as nitrogen and phosphate between living and non-living organisms.

“Excessive nitrogen leads to soil and air pollution, drives biodiversity loss, pollutes coastal marine waters and catchments and increases the level of nitrous oxide and other nitrogen gases in the atmosphere,” said Professor Sayer.

He said estimates varied, but it was generally thought the use of nitrogen fertiliser in agriculture increased by about 800% from 1960 to 2000.

Professor Sayer said the amount of phosphate used on agricultural land was now two or three times above that expected to occur naturally, fuelled by the mining of phosphate deposits for use as fertiliser.

“This leads to run-off which dumps nutrients into freshwater and estuarine systems and accelerates the growth of plants and algae which choke off the oxygen supply in the water.”

He said with the global demand for food due to rising population and changing diets, demand for phosphate could increase by 50 –100% by 2050.

Professor Sayer said agriculture was also mostly responsible for breaching the limit on biosphere integrity – genetic and functional biodiversity.

“We measure genetic diversity loss in terms of extinctions per million species-years. The fossil record tells us this number was 0.1 to 1 in the past, and we think 10 would be a realistic limit, beyond which we are getting into dangerous territory.”

He said the current figure was 100, with future projections in the order of 1,000 – 10,000.

“Functional diversity, by contrast, is essentially the maintenance of functioning ecosystems with their full complement of interacting species. It looks like we are past a safe limit here across nearly 60 percent of the world’s land surface, with the destruction of forests to provide agricultural land a major factor.”

Professor Sayer said as well as the two limits that had already been breached, three of the other nine planetary boundaries were in the high-risk zone – with agriculture a major driver in all of them.

“You have to look at this in light that of the fact human population is predicted to reach about 9 billion by 2050, and as people get richer they eat more food overall, particularly meat,” he said.

Professor Sayer said there were solutions to all of the problems, such as more efficient use of nitrogen and phosphate and a dedicated effort to stop forests being turned into farmland. But he said the time was long-past for half-measures.

“There’s no doubt that more land will need to be brought under cultivation, but this will need to be carefully selected and managed. Nothing less than a radically transformed system is needed, with numerous changes made to all aspects of production, with more attention to landscape-level management, and with changes made to all aspects of the broader food system.”

Link to full paper here.

Background

The nine Planetary Boundaries :

1. Land-system change (increasing risk)

2. Freshwater use (increasing risk)

3. Biogeochemical flows (breached)

4. Change in biosphere integrity (breached)

5. Climate change (increasing risk)

6. Ocean acidification (safe)

7. Stratospheric ozone depletion (safe)

8. Atmospheric aerosol loading (safe)

9. Introduction of novel entities (safe)