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The Unintended Consequences of Reducing Food Waste

By Iain Gordon

With the global human population continuing to outpace agricultural production, we may need to reduce the amount of food that we waste. But what will be the unintended consequences for wildlife that depend on food waste?

Feeding the growing global population is a significant challenge. Indeed, it is expected that we’ll need to produce 70% more food than we do today to feed the estimated 10 billion people who will inhabit our planet in 2050.

The recent debate about how to feed our growing population has focused on increasing production from agricultural systems. This does not portent well for nature. Agriculture does not have a good relationship with biodiversity, which is being lost as land is converted to crops and pastures; air, water and soils are polluted by excesses in nitrogen and phosphorus from fertilisers; and species of insects and birds are killed directly or indirectly by pesticides.

There is another way: reduce the amount of agricultural produce and food we waste. It’s estimated that 30–50% of the 4 billion tonnes of food produced each year is wasted. In developing countries this tends to happen before the crop is harvested or because of poor storage; in developed countries food is thrown away from supermarkets or the fridge once it is past its “sell-by” date or thrown into the bin after the meal in the home.

In North America and Europe this amounts to roughly 95–115 kg/capita/year. Australians throw out about 4 million tonnes of food per year. Much of it goes to landfill.

Reducing food waste would reduce pressure on the agricultural production system, possibly limiting the increase in agricultural land needed to supply the extra food. Of course, this would have a significant knock-on benefit for biodiversity.

However, we need to think about the unintended consequences of reducing waste for the species that have become reliant on our waste. These species are, in effect, part of food webs that are supplemented by humans.

For example, populations of western gulls (Larus occidentalis) in North America’s west have increased significantly over recent years, primarily because of food supplementation from landfill, and this is thought to have had negative impacts on threatened steelheads (a fish). By reducing waste sent to landfill we may see a decline in gulls there, potentially reducing their impact on other species, but they may equally divert their predation pressure to other vulnerable species in the ecosystem.

We should also be alert to species that have become so reliant on food waste that it is now their main source of food. In Australia, species such as the white ibis (Threskiornis moluccus) has become heavily reliant on landfill sites adjacent to our big cities, while the populations in their natural range have declined because of loss of habitat and drought. Ibises may be a pest and potential harbourers of disease, such as Salmonella bacteria, but removing waste may put their populations in jeopardy.

Let’s learn from history. In Shakespearean times the red kite (Milvus milvus) was classed as a pest that fed on waste in the streets of London. Shakespeare wrote in The Winter’s Tale: “when the kite builds, look to lesser linen,” because the birds used cloth for nesting material. Persecution and reductions in waste associated with improved sanitation and food storage saw the red kite become almost extinct in the UK in the early 20th century. Only recently, following high profile reintroductions, are kites commonly seen in parts of the English countryside.

Likewise, when bovine spongiform encephalitis hit Europe, regulations required farmers to remove the carcasses of dead livestock from fields. In Southern Europe, this led to dramatic reductions in populations of bearded vultures (Gypaetus barbatus) and griffon vultures (Gyps fulvus) that had become reliant on livestock carcasses because of declines in populations of native deer. Only when vulture “restaurants” were set up to provide alternative sources of carrion did the vulture populations show signs of recovery.

Reducing food waste could benefit biodiversity but it may also create profound perturbations in food webs that are founded upon human food waste. We do not know what the consequences will be, but they may not all be positive for biodiversity.


Professor Iain Gordon is Deputy Vice Chancellor – Tropical Environments & Societies at James Cook University.