Battling the seven-headed hydra: Crassula control in Europe

8 11 2016
Hydra. Seba Albertus (1734-1765). Image from Wellsome Trust

Hydra. Seba Albertus (1734-1765). Image from Wellsome Trust

A contribution by Claire Wordley of Conservation Evidence.

The Australian swamp stonecrop (Crassula helmsii) is a small, unassuming looking plant with incredible resilience. It can survive both baking heat and freezing cold; it can live underwater, on the water’s surface and on land; it can survive being dried out, bleached and sprayed with hot foam; and it can regenerate from tiny fragments. Unfortunately, in the UK and elsewhere in Europe it is an invasive species, choking the oxygen from ponds and shading out other plants with knock-on effects for entire freshwater ecosystems.

Swamp stonecrop, also known as New Zealand pigmyweed, was first introduced to the UK from Tasmania in 1911 and sold in garden centres from 1927 as an ornamental pond oxygenator. Shockingly, despite being documented as an invasive plant in New Forest ponds as early as 1976, its sale in the UK was only banned in 2014. Crassula appears to be spread mostly by people, whether deliberately or accidentally; it appears to be concentrated around car parks, residential areas and areas where equipment such as fishing gear is likely to have come from an infected site. Nearly 20% of 700 UK waterbodies surveyed contained the weed. Since every 10% increase in Crassula corresponds to a 5% decrease in native vegetation, and negative effects of Crassula invasion have been documented for zooplankton, macro-invertebrates and fish, with possible negative impacts on amphibians as well, control and ideally eradication is clearly needed. But what works to destroy this superweed?

Killing the hydra

Crassula helmsii (photo by Benjamin Blondel)

Crassula helmsii (photo by Benjamin Blondel)

Like the seven-headed hydra of legend, Crassula helmsii seems able to regenerate after even harsh treatment and being shattered into tiny pieces. Documenting clearly what works to control this beast – and what does not – is critical. This work has recently been completed by Conservation Evidence at the University of Cambridge, as part of an ongoing series on controlling freshwater invasives. The team has worked to collect all the evidence on different ways of killing Crassula, and experts have scored these for their effectiveness (or otherwise).

One of the most effective ways to knock back Crassula appears to be applying herbicides, particularly glyphosate and diquat or diquat alginate. While each of these performed well to reduce Crassula in many trials – and the use of glyphosate and diquat together led to a 98% reduction in one trial – there are concerns that while the medicine could cure the disease, it could kill the patient. One study in the New Forest noted that native plant cover fell in the treatment sites at a greater rate than in the control sites, and glyphosate appears to be toxic to amphibians. There might also be adverse effects on some bird species, although this could be due more to habitat-level changes than direct toxicity, because other birds appeared to benefit from wetlands being sprayed with glyphosate. Read the rest of this entry »





World’s greatest conservation tragedy you’ve probably never heard of

13 10 2016

oshiwara_riverI admit that I might be stepping out on a bit of a dodgy limb by claiming ‘greatest’ in the title. That’s a big call, and possibly a rather subjective one at that. Regardless, I think it is one of the great conservation tragedies of the Anthropocene, and few people outside of a very specific discipline of conservation ecology seem to be talking about it.

I’m referring to freshwater biodiversity.

I’m no freshwater biodiversity specialist, but I have dabbled from time to time, and my recent readings all suggest that a major crisis is unfolding just beneath our noses. Unfortunately, most people don’t seem to give a rat’s shit about it.

Sure, we can get people riled by rhino and elephant poaching, trophy hunting, coral reefs dying and tropical deforestation, but few really seem to appreciate that the stakes are arguably higher in most freshwater systems. Read the rest of this entry »





Biowealth

24 02 2016

frogWhile I’ve blogged about this before in general terms (here and here), I thought it wise to reproduce the (open-access) chapter of the same name published in late 2013 in the unfortunately rather obscure book The Curious Country produced by the Office of the Chief Scientist of Australia. I think it deserves a little more limelight.

As I stepped off the helicopter’s pontoon and into the swamp’s chest-deep, tepid and opaque water, I experienced for the first time what it must feel like to be some other life form’s dinner. As the helicopter flittered away, the last vestiges of that protective blanket of human technological innovation flew away with it.

Two other similarly susceptible, hairless, clawless and fangless Homo sapiens and I were now in the middle of one of the Northern Territory’s largest swamps at the height of the crocodile-nesting season. We were there to collect crocodile eggs for a local crocodile farm that, ironically, has assisted the amazing recovery of the species since its near-extinction in the 1960s. Removing the commercial incentive to hunt wild crocodiles by flooding the international market with scar-free, farmed skins gave the dwindling population a chance to recover.

redwoodConservation scientists like me rejoice at these rare recoveries, while many of our fellow humans ponder why we want to encourage the proliferation of animals that can easily kill and eat us. The problem is, once people put a value on a species, it is usually consigned to one of two states. It either flourishes as do domestic crops, dogs, cats and livestock, or dwindles towards or to extinction. Consider bison, passenger pigeons, crocodiles and caviar sturgeon.

As a conservation scientist, it’s my job not only to document these declines, but to find ways to prevent them. Through careful measurement and experiments, we provide evidence to support smart policy decisions on land and in the sea. We advise on the best way to protect species in reserves, inform hunters and fishers on how to avoid over-harvesting, and demonstrate the ways in which humans benefit from maintaining healthy ecosystems. Read the rest of this entry »





Game bird madness

4 11 2015

Gamecart_largeI just returned to Paris after a brief visit to the University of Aberdeen over the weekend. My hosts, Xavier Lambin and Beth Scott, were not only marvellously welcoming, I also learned a lot about the travesty that is game bird management in the United Kingdom, and especially in Scotland.

As you might already know, the Great Britons are a little cuckoo for birds — I’d even wager that the country produces more twitchers than any other country on Earth. The plus side is that there are few national taxa better censused and studied that British birds, because so many non-scientists get into the spirit of data collection. Hell, I’ve even had a play with some of their datasets.

The other side of this bird madness is not so good — I’m talking about the massive biomass of game birds reared, released and shot every year in the United Kingdom. It’s not the hunting per se with which I take issue, it’s the insane manipulation of an entire ecosystem for the benefit of a few species. Read the rest of this entry »





Killing the Koala and Poisoning the Prairie

19 10 2015

Cover-Bradshaw&Ehrlich-final

Man and the environment are meant for each other” — Tony Abbott, former Prime Minister of Australia (2014)

I know the human being and the fish can co-exist peacefully” — George W. Bush, former President of the USA (2000)

It. Has. Finally. Been. Published.

Yes, my new book with Paul Ehrlich, published by University of Chicago Press, is now available to purchase in book shops and online distributors around the world. The blog post today is a little explanatory synopsis of why we wrote the book and what it contains, but of course the real ‘meat’ is in the book. I hope you enjoy it.

In Australia, you can purchase the hard copy through Footprint Books, and the Kindle version at Amazon Australia. I also suggest that Australians might find the best deals through Booko. Electronic versions are also available through Kobo and Google Play. In the US you can order directly from University of Chicago Press, Amazon, Barnes & Noble, and many other book sellers. In the UK and Europe, the book is available from your country’s Amazon distributor. I imagine many chain and independent book sellers will be carrying the book by now, or will be soon.

My deepest thanks to all those who made it possible.

Our chance meeting in 2009 at Stanford University turned out to be auspicious, not least of which because of the publication this week of our co-authored book, Killing the Koala and Poisoning the Prairie. Australia, America and the Environment by University of Chicago Press. As a mid-career ecologist (Bradshaw) based at the University of Adelaide, it was indeed an honour to meet one of the most famous scientists (Ehrlich) in my field. With a list of books and hundreds of scientific papers under his belt, Ehrlich has been tackling major environmental issues since the 1960s. Ehrlich also has a long-time interest in Australia, having visited nearly every year during the last four decades and experienced more of the country than most Australians. Together we have observed firsthand the similarities and differences of Australia and the US, and the eyes we see through are trained as those of environmental scientists and evolutionary biologists.

So why write a book about the environmental tragedies currently unfolding in two completely different countries at opposite ends of the Earth? As it turns out, Australia and the US have much more in common environmentally than one might think, and not necessarily in a good way. Despite our vastly different floras and faunas, population densities, histories of human colonisation and soil productivities, there is an almost spooky similarity in the environmental and political problems both our countries are now experiencing. As such, we have a lot to learn about avoiding each other’s mistakes.

Ausmerica

Australia and the contiguous US are roughly equivalent in land area, both cultures are derived originally and principally from what is now the United Kingdom, and both are examples of super-consuming, super-wasting, wealthy, literate countries. Both countries also have environmental footprints that exceed most other countries on Earth, with some of the world’s highest per capita rates of greenhouse-gas emissions, water consumption, species extinctions and deforestation.  Read the rest of this entry »





Australia’s perfect storm of negligence

17 03 2015

If, for the purposes of some sick and twisted thought experiment, you were to design policies that would ensure the long-term failure of a wealthy, developed nation, you wouldn’t have to look farther than Australia’s current recipe for future disaster. I’m not trying to be provocative, but the warning signs are too bold and flashy to ignore. Let’s just run through some of the main ones:

1. As the lambasted and thoroughly flawed 2015 Intergenerational Report clearly demonstrates, our current government has no idea about the future threats of climate change. Dragged kicking and screaming into only a symbolic recognition of some ‘distant and currently irrelevant problem’, the Abbott-oir and his intergenerational criminals are well known for killing the carbon-pricing scheme, dismantling the Department of Climate Change, pulling out of major international talks on climate-change mitigation and installing a half-arsed, ineffective policy that will do nothing to stem our emissions. Combine that with comments like “coal is good for humanity“, and it’s easy to see how our current leaders have little idea about the future mess they’re creating.

2. Not content just to kick the shit out of any meaningful climate action, our government has also turned its back on any renewable energy target, and facilitated the fossil-fuel barons to dig more coal out of the ground. While South Australia’s Royal Commission on the nuclear fuel cycle is a welcome candle in the climate change-mitigation darkness here, it is far from becoming a national priority any time soon.

3. As has been well documented, the Abbott-oir ship of fools has also done whatever it can to turn back decades of environmental protections in less than six months of taking office. Everything from opening up national parks for exploitation, failing to protect marine sanctuaries, limiting environmental checks to promoting logging in World Heritage Areas, there is little room for hope that our crumbling environmental system will improve at all in the near to long term. Read the rest of this entry »





What’s in a name? The dingo’s sorry saga

30 01 2015

bad dingoThe more I delve into the science of predator management, the more I realise that the science itself takes a distant back seat to the politics. It would be naïve to think that the management of dingoes in Australia is any more politically charged than elsewhere, but once you start scratching beneath the surface, you quickly realise that there’s something rotten in Dubbo.

My latest contribution to this saga is a co-authored paper led by Dale Nimmo of Deakin University (along with Simon Watson of La Trobe and Dave Forsyth of Arthur Rylah) that came out just the other day. It was a response to a rather dismissive paper by Matt Hayward and Nicky Marlow claiming that all the accumulated evidence demonstrating that dingoes benefit native biodiversity was somehow incorrect.

Their two arguments were that: (1) dingoes don’t eradicate the main culprits of biodiversity decline in Australia (cats & foxes), so they cannot benefit native species; (2) proxy indices of relative dingo abundance are flawed and not related to actual abundance, so all the previous experiments and surveys are wrong.

Some strong accusations, for sure. Unfortunately, they hold no water at all. Read the rest of this entry »








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