06 Jan 2016: Report

Unnatural Balance: How Food
Waste Impacts World’s Wildlife

New research indicates that the food discarded in landfills and at sea is having a profound effect on wildlife populations and fisheries. But removing that food waste creates its own ecological challenges.

by richard conniff

The world wastes more than $750 billion worth of food every year — 1.6 billion tons of food left in farm fields, sent to landfills, or otherwise scattered across the countryside, plus another seven million tons of fishery discards at sea. That waste has gotten a lot of attention lately, mostly in terms of human hunger.

Hardly anyone talks about what all that food waste is doing to wildlife. But a growing body of evidence suggests that our casual attitude about waste

Wikimedia Commons
Discarded food can lead to overpopulation of seagulls and other animals, which can affect other wildlife populations.
may be reshaping the way the natural world functions across much of the planet, inadvertently subsidizing some opportunistic predators and thus contributing to the decline of other species, including some that are threatened or endangered.

A new study in the journal Biological Conservation looks, for instance, at California’s Monterey Bay, where the threatened steelhead trout population has declined by 80 to 90 percent over the past century. Efforts to restore the species along the Pacific Coast have focused on major initiatives like the recent demolition of a dam that had blocked access to critical steelhead breeding grounds on the Carmel River, which empties into Monterey Bay.

But a team of co-authors led by Ann-Marie Osterback, a marine ecologist at the University of California-Santa Cruz, suspects that garbage and fishery discards might also play an underrated part in the problem. The hypothesis is that local food wastes inadvertently subsidize Western gulls in the Monterrey Bay area, and these gulls in turn prey on the juvenile steelhead trout.

The dramatic decline in steelhead numbers would normally mean that fish-eating birds around Monterey Bay would have to move down the food chain to survive. That’s what’s happened to Brandt’s cormorants and marbled murrelets, and their populations have declined as a result.
Animals have been picking up the food scraps forever, but nothing in history approaches the scale of modern food waste.
But according to Osterback, the number of gulls have doubled or quadrupled in different parts of the bay just since the 1980s — thanks to a steady diet of landfill garbage and fishery discards. Osterback and her co-authors found that each individual gull now eats less steelhead than in the past, but the combination of a greatly increased gull population and a severely reduced run of steelhead trout adds up to a dramatic rise in predation pressure. She estimates that the gulls may eat up to 30 percent of juvenile steelhead en route to the sea.

Likewise, yellow-legged gulls subsidized by food wastes in the western Mediterranean, threaten Auduoin’s gulls, European storm petrels, and other vulnerable seabirds through increased predation pressure. Off the coast of Alaska, fishery-subsidized killer whales imperil near-threatened Steller sea lions. And on the western side of the Mojave Desert, common ravens and coyotes that feed on garbage from nearby communities are jeopardizing the recovery of the threatened desert tortoise.

“Ravens scavenge when refuse or carrion are available but they are also capable hunters,” a study in Ecology found. The researchers put out 100 dummy models of juvenile desert tortoises and found that ravens attacked 29 of them over a two-month period. Other studies have linked subsidized ravens to the decline of such threatened or endangered species as marbled murrelets, California least terns, snowy plovers, San Clemente loggerhead shrikes, and sandhill cranes.

Animals have of course been picking up the food scraps we leave behind forever — or at least long enough to change the course of their evolution. That’s how certain wolves evolved into domestic dogs. But nothing in the history of the planet approaches the scale of modern food waste, in farm fields, on streets and beaches, in landfills, and strewn behind fishing boats.
Controlling garbage is not new as a conservation tool, but it has sparked one of the nastiest fights in U.S. conservation.

This abundance of garbage is also a factor in the resurgence of brown bears (population 17,000) and wolves (population 11,000) in modern Europe. Garbage is also the main reason leopards have been able to adapt to living in and around major cities in India. They prey on other animals that scavenge from abundant garbage — dogs, pigs, goats, and rats — and they also feed directly on butchered carcasses discarded in the open.

Removing or controlling garbage is not new as a conservation tool. The U.S. National Park Service did it in the 1970s at Yellowstone National Park, closing dumps and ending the artificial feeding of bears there. But it also sparked one of the nastiest fights in the history of U.S. conservation, especially as the park service began killing or translocating “incorrigible” bears. Cut off from their familiar food sources, the grizzlies struggled and their population declined for a time. Gradually, though, the bears shifted to a more natural diet, moved away from the roads, and ultimately flourished. The Yellowstone grizzly population has roughly quadrupled since the end of artificial feeding in the 1970s, to about 700 bears in 2014.

Measures to address the garbage problem on a broader scale today will likely be at least as challenging. On the one hand, such measures can reduce populations of subsidized predators without the controversy caused by programs to kill or relocate nuisance animals. A study in France demonstrated that closing a dump led to a 49-percent decline in fertility of herring gulls, which are also opportunistic predators. Another study in the western Mediterranean found that a temporary moratorium on trawling had a dramatic impact on gull reproduction, by removing the discards that can otherwise make up as much as 73 percent of their diet.

But when the European Union was debating a ban on fishery discards in 2013, ecologists warned of “unforeseen knock-on consequences.” They pointed out that 52 percent of seabird species worldwide now scavenge fishery discards to some degree. A ban would leave some species hungry,


The Big Waste: Why Do We
Throw Away So Much Food?

e360 food waste video
In an e360 video, filmmaker Karim Chrobog looks at the staggering amount of food wasted in the U.S. – a problem with major human and environmental costs. The video focuses on Washington, D.C., which has taken steps to see that food ends up with those who need it rather than in landfills.
and some might turn to eating other bird species to survive.

The EU is currently moving ahead with its ban in three phases. Now in its second year, it’s too soon to say how it is affecting seabirds. Daniel Oro, a fisheries ecologist at the Mediterranean Institute for Advanced Studies on Majorca, worries about the potential effect on the critically endangered Balearic shearwater, a seabird that frequently depends on fishery discards while rearing its young. “We are going to have smaller populations of Balearic shearwaters, that’s very clear,” said Oro. “Populations suffer a period of readapting to the new system. Many individuals are going to die, as happened with bears at Yellowstone.”

But Oro also considers the cleanup essential. Before the closing of the only dump on Majorca, he said, researchers found that many of the birds there “were low-quality individuals. They had physical problems, they had lung problems, and other diseases that were not easily seen from the outside.” The dump supported birds that natural selection would have weeded out in the wild.

Cleaning up our food waste mess and shifting wildlife populations back to natural resources increases competition and ultimately “benefits higher quality individuals,” said Oro, “so that’s good news.” But, as at Yellowstone, he acknowledged, getting there will be painful.

POSTED ON 06 Jan 2016 IN Biodiversity Business & Innovation Energy Oceans Policy & Politics Pollution & Health Sustainability Asia 


California Safe Soil (www.calsafesoil.com) has a great new technology to recycle food supermarkets can no longer sell or donate into a liquid fertilizer called Harvest to Harvest (H2H). We use heat, mechanical action and enzymes to convert proteins, fats and carbohydrates into amino acids, organic acids and simple sugars that can be delivered through farm irrigation lines directly into the root zone to stimulate life in diverse soil organisms. Increasing soil organic matter improves soil health and increases crop yields.

There are scientifically sustainable solutions to the food waste problem - they just need to be implemented.
Dan Morash (Y'78)
Posted by Dan Morash on 06 Jan 2016

Thanks Richard for this interesting blog.

Our research group works at Año Nuevo Island, CA, the breeding colony of the Western Gulls that may be eating steelhead in the Osterback study. The assertion that "the number of gulls have doubled or quadrupled in different parts of the bay just since the 1980s" is based on a citation of our data (Carle et al. 2014) in the Osterback paper.

I would like to clarify that, although it is true that the population of Western Gulls has indeed risen greatly since the 1970's and 1980's at Año Nuevo, it is misleading to assume that all of this growth was fueled by human food subsidy, or even that the current population is necessarily greater than historical populations (i.e. 1800s or earlier). The Western Gull population at Año Nuevo grew from around 100-200 nests in the 70's and peaked at around 1200 nests in 2005- a lot of growth. But the 1970's numbers were at probably the lowest ebb of population, after around 100 years of disturbance and direct persecution during the mid 1800's- mid 1900's when a manned lightkeeper's station operated on Año Nuevo Island. There are no data from Año Nuevo pre-1970's, but at the Farallon Islands its well documented that the gull population was drastically reduced during the 1800's and early 1900's and only recovered when the islands were protected. Año Nuevo was protected in the 1960's and the gull population has recovered since. This may have more to do with the growth we've seen than the trash. During the 1980's-1990's increase in gull population at Año Nuevo and other nearshore colonies, there was a major decrease at the offshore Farallones, so the overall popualation in central California may have remained stable.

What's more, the Western Gull population has been annually declining at Año Nuevo since its peak in 2005. There were only 643 nests in 2015 compared with 1234 nests in 2005. Many factors could be contributing to this decline, most probably lowered availability of natural prey such as krill and forage fishes. Similar declines are being seen at the Farallones, indicating a larger scale pattern than just local landfill management.

Finally, there are several published studies showing that Western Gull reproduction is actually worse, not better, for individuals that eat a lot of trash (see multiple papers from Alcatraz Island by Pierrotti and Annett). This implies that contrary to intuition, trash may actually not help subsidize population growth in this species after all. Trash may buffer adult survival in years of poor natural food availability but this has not been thoroughly studied.

Also, the assertion that Brandt's Cormorants have declined due to reduced steelhead numbers is not entirely accurate. Though these cormorants do eat salmon sometimes, they are more influenced by species like anchovy and juvenile rockfishes. Brandt's Cormorant population trajectory is somewhat similar to the gulls'--they increased from 2 nests in 1992 to over 2,000 nests in the mid-2000's: a thousand-fold increase! Similar to the gulls, their populations dropped at the Farallones as the nearshore populations grew.

We certainly support better landfill management, which would have positive ecosystem-wide impacts. We regularly see Western Gulls dying from botulism and poisons picked up from human sources. However, the narrative that the Western Gull population has unnaturally exploded, causing them to be an unnaturally large threat to the steelhead, is more nuanced than presented here.

Ryan Carle
Program Manager
Año Nuevo Island Seabird Research and Conservation
Oikonos Ecosystem Knowledge

Posted by Ryan Carle on 08 Jan 2016


Comments are moderated and will be reviewed before they are posted to ensure they are on topic, relevant, and not abusive. They may be edited for length and clarity. By filling out this form, you give Yale Environment 360 permission to publish this comment.

Email address 
Please type the text shown in the graphic.

richard conniffABOUT THE AUTHOR
Richard Conniff is a National Magazine Award-winning writer whose articles have appeared in Time, Smithsonian, The Atlantic, National Geographic, and other publications. He is the author of several books, including The Species Seekers: Heroes, Fools, and the Mad Pursuit of Life on Earth. In previous articles for Yale e360, he has written about Rachel Carson's battle against the pesticide DDT and reported on the role of electric power line corridors in conservation.



How Nations Are Chipping
Away at Their Protected Lands

Winning protected status for key natural areas and habitat has long been seen as the gold standard of conservation. But these gains are increasingly being compromised as governments redraw park boundaries to accommodate mining, logging, and other development.

How Ocean Noise Pollution
Wreaks Havoc on Marine Life

Marine scientist Christopher Clark has spent his career listening in on what he calls “the song of life” in the world’s oceans. In an interview with Yale Environment 360, he explains how these marine habitats are under assault from extreme—but preventable—noise pollution.

How Forest Loss Is Leading
To a Rise in Human Disease

A growing body of scientific evidence shows that the felling of tropical forests creates optimal conditions for the spread of mosquito-borne scourges, including malaria and dengue. Primates and other animals are also spreading disease from cleared forests to people.

Beyond the Oregon Protests:
The Search for Common Ground

Thrust into the spotlight by a group of anti-government militants as a place of confrontation, the Malheur wildlife refuge is actually a highly successful example of a new collaboration in the West between local residents and the federal government.

How ‘Natural Geoengineering’
Can Help Slow Global Warming

An overlooked tool in fighting climate change is enhancing biodiversity to maximize the ability of ecosystems to store carbon. Key to that strategy is preserving top predators to control populations of herbivores, whose grazing reduces the amount of CO2 that ecosystems absorb.


MORE IN Reports

As Drought Grips South Africa,
A Conflict Over Water and Coal

by keith schneider
Facing one of the worst droughts in memory, South Africa’s leaders have doubled down on their support of the water-intensive coal industry. But clean energy advocates say the smartest move would be to back the country’s burgeoning wind and solar power sectors.

Saving Amphibians: The Quest
To Protect Threatened Species

by jim robbins
The decline of the world’s amphibians continues, with causes ranging from fungal diseases to warmer and drier climates. Now, researchers are looking at ways to intervene with triage measures that could help save the most vulnerable populations.

How Rising CO2 Levels May
Contribute to Die-Off of Bees

by lisa palmer
As they investigate the factors behind the decline of bee populations, scientists are now eyeing a new culprit — soaring levels of carbon dioxide, which alter plant physiology and significantly reduce protein in important sources of pollen.

Can Uber-Style Buses Help
Relieve India's Air Pollution?

by jason overdorf
India’s megacities have some the deadliest air and worst traffic congestion in the world. But Indian startups are now launching initiatives that link smart-phone apps and private shuttle buses and could help keep cars and other motorized vehicles off the roads.

Trouble in Paradise: A Blight
Threatens Key Hawaiian Tree

by richard schiffman
The ʻohiʻa is Hawaii’s iconic tree, a keystone species that maintains healthy watersheds and provides habitat for numerous endangered birds. But a virulent fungal disease, possibly related to a warmer, drier climate, is now felling the island’s cherished 'ohi'a forests.

Climate Change Adds Urgency
To Push to Save World’s Seeds

by virginia gewin
In the face of rising temperatures and worsening drought, the world’s repositories of agricultural seeds may hold the key to growing food under increasingly harsh conditions. But keeping these gene banks safe and viable is a complicated and expensive challenge.

As World Warms, How Do We
Decide When a Plant is Native?

by janet marinelli
The fate of a tree planted at poet Emily Dickinson's home raises questions about whether gardeners can — or should — play a role in helping plant species migrate in the face of rising temperatures and swiftly changing botanical zones.

With New Tools, A Focus
On Urban Methane Leaks

by judith lewis mernit
Until recently, little was known about the extent of methane leaking from urban gas distribution pipes and its impact on global warming. But recent advances in detecting this potent greenhouse gas are pushing U.S. states to begin addressing this long-neglected problem.

Is Climate Change Putting
World's Microbiomes at Risk?

by jim robbins
Researchers are only beginning to understand the complexities of the microbes in the earth’s soil and the role they play in fostering healthy ecosystems. Now, climate change is threatening to disrupt these microbes and the key functions they provide.

As Electric Cars Stall, A Move
To Greener Trucks and Buses

by cheryl katz
Low gasoline prices and continuing performance issues have slowed the growth of electric car sales. But that has not stymied progress in electrifying larger vehicles, including garbage trucks, city buses, and medium-sized trucks used by freight giants like FedEx.

e360 digest
Yale Environment 360 is
a publication of the
Yale School of Forestry
& Environmental Studies


Donate to Yale Environment 360
Yale Environment 360 Newsletter



About e360
Submission Guidelines

E360 en Español

Universia partnership
Yale Environment 360 articles are now available in Spanish and Portuguese on Universia, the online educational network.
Visit the site.


e360 Digest
Video Reports


Business & Innovation
Policy & Politics
Pollution & Health
Science & Technology


Antarctica and the Arctic
Central & South America
Middle East
North America

e360 VIDEO

Tribal people and ranchers join together to stop a project that would haul coal across their Montana land.
Watch the video.


The latest
from Yale
Environment 360
is now available for mobile devices at e360.yale.edu/mobile.


An aerial view of why Europe’s per capita carbon emissions are less than 50 percent of those in the U.S.
View the photos.

e360 VIDEO

The 2015 Yale e360 Video Contest winner documents a Northeastern town's bitter battle over a wind farm.
Watch the video.

e360 VIDEO

Food waste
An e360 video series looks at the staggering amount of food wasted in the U.S. – a problem with major human and environmental costs.
Watch the video.

e360 VIDEO

Colorado wildfires
An e360 video goes onto the front lines with Colorado firefighters confronting deadly blazes fueled by a hotter, drier climate.
Watch the video.


A three-part series Tainted Harvest looks at the soil pollution crisis in China, the threat it poses to the food supply, and the complexity of any cleanup.
Read the series.