Our directory of things of interest

University Directory

Weed killers: endangered owls in California

Weed killers: endangered owls in California
01 Mar
2018
Threatened Californian owls are suffering from digesting rat poison administered to the state’s thousands of marijuana farms

Marijuana is proving to be a health hazard, although not for the reasons one would assume. Since the start of the year, the private cultivation of marijuana crops has been legal in California, making it the fifth US state to permit the practice. Business is booming; Humboldt County alone, in the north of the state, is home to at least 4,500 – and potentially as many as 15,000 – plantations, and there is an expectation that numbers will continue to rise. However, at present the majority of these remain unlicensed and unregulated, even despite the recent legalisation passing.

Recent studies on owls found deceased in remote locations across Humboldt and neighbouring Mendocino and Del Norte Counties is focusing attention on the ecological impact of these farms. For example, 70 per cent of northern spotted owls – which are in decline in both range and population, and are consequently listed as ‘threatened’ under the Endangered Species Act – tested positive for various anticoagulant rodenticides, utilised to control rat populations within these farms.

Jack Dumbacher and owl collection 5 2017 California Academy of Sciences.jpg

By preventing the recycling of vitamin K, rodenticides cause a series of clotting and coagulation problems in both birds and mammals, followed by uncontrollable internal bleeding. For owls feeding naturally at forest edges, which unfortunately often also happen to mark the edges of these plantations, their dead rat dinners could potentially be their own death sentence (the studied birds in question were judged to have died of causes ranging from vehicle strikes to predation, not poison).

‘Sublethal anticoagulant rodenticide impacts vary from species to species, and also within individuals,’ explains Mourad Gabriel, a research faculty member at the UC Davis School of Veterinary Medicine. ‘We detected levels in our study that have been reported as benign in other owls, but other studies have shown these levels to be lethal, or having a negative impact in other owls or raptors. So as you can see it becomes a case-by-case scenario.’

Gabriel believes that, eventually, the legal market for marijuana will drive out these unregulated plantations and their overuse of rodenticides, but raises concerns about how long this might take. ‘We have empirical evidence of landscape contamination, and others have demonstrated habitat fragmentation,’ he adds. ‘The northern spotted owl is not increasing in population numbers, and there is consideration of up-listing this species to “endangered”.’

This was published in the March 2018 edition of Geographical magazine

geo line break v3

Free eBooks - Geographical Newsletter

Get the best of Geographical delivered straight to your inbox by signing up to our weekly newsletter and get a free collection of eBooks!

geo line break v3

Related items

Subscribe to Geographical!

geo line break v3

Free eBooks - Geographical Newsletter

Sign up for our weekly newsletter today and get a FREE eBook collection!

geo line break v3

University of Winchester

geo line break v3

EDUCATION PARTNERS

Aberystwyth University University of Greenwich The University of Derby

TRAVEL PARTNERS

Ponant

Silversea

Travel the Unknown

DOSSIERS

Like longer reads? Try our in-depth dossiers that provide a comprehensive view of each topic

  • The Human Game – Tackling football’s ‘slave trade’
    Few would argue with football’s position as the world’s number one sport. But as Mark Rowe discovers, this global popularity is masking a sinister...
    Essential oil?
    Palm oil is omnipresent in global consumption. But in many circles it is considered the scourge of the natural world, for the deforestation and habita...
    The Nuclear Power Struggle
    The UK appears to be embracing nuclear, a huge U-turn on government policy from just two years ago. Yet this seems to be going against the grain globa...
    Hung out to dry
    Wetlands are vital storehouses of biodiversity and important bulwarks against the effects of climate change, while also providing livelihoods for mill...
    The true cost of meat
    As one of the world’s biggest methane emitters, the meat industry has a lot more to concern itself with than merely dietary issues ...

MORE DOSSIERS

NEVER MISS A STORY - Follow Geographical on Social

Want to stay up to date with breaking Geographical stories? Join the thousands following us on Twitter, Facebook and Instagram and stay informed about the world.

More articles in NATURE...

Climate

Most plants thicken their leaves in response to higher carbon…

Climate

Not just the preserve of flatulent cows, methane is causing…

Climate

As the United States’ Supreme Court delays a landmark climate…

Geophoto

Of Britain's 15 national parks, the New Forest is probably…

Energy

The Treasury has announced that it is considering imposing a…

Tectonics

Major earthquakes are triggering seismic activity half the world away

Climate

Marco Magrini finds that a warming world also means a…

Wildlife

Unchecked tourism is potentially reducing the number of cheetah cubs that…

Oceans

A relocated military base in Okinawa, Japan will cause ‘irreversible’…

Climate

The ongoing recovery of the planet’s ozone layer is being…

Oceans

The Ocean Cleanup has launched System 001, a floating barrier…

Nature

New videos reveal how plants respond to wounds, sending forth…

Geophoto

The recent heatwave had everyone longing for a drop of…

Wildlife

The demand for horseshoe crab blood – vital for testing…

Climate

One of the problems in getting accurate climate science out…

Wildlife

Italy is divided over the future of its wolves and…

Energy

A Scottish tidal power project in the Pentland Firth has…

Oceans

The world’s first full global analysis of beaches reveals the…

Geophoto

With the recent Saddleworth Moor fire, it can be easy…

Wildlife

Whale sharks have been found to not travel far from…