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Draft ERF method: Measurement of soil carbon sequestration in agricultural systems
Draft ERF method: Measurement of soil carbon sequestration in agricultural systems
Australia-led tidal energy project sets new production records
100 years ago: woolly bear caterpillars obey the law
Originally published in the Manchester Guardian on 4 September 1917
September 3
“Woolly bears,” in a fearful hurry, race across the road; they look as if they meant business or feared the wheel of passing vehicle or heedless boot. But the caterpillar knows nothing of danger, but merely acts as heredity has taught it; it must obey laws or go under in the struggle. Most insects need a wide distribution, for too restricted a feeding area may bring famine or degeneration; in one or other of their stages insects must get to a distance from congested districts or from ravaged food-plants. Naturally this distribution or migration takes place with many insects when, in their perfect stage, they are provided with wings, but some moths are slow-flying and lethargic, too busy with nectar-sipping and egg-laying to travel far, and in these the caterpillars make the journeys, getting over as much ground as they can before they find it necessary to spin cocoons.
Related: Why gardeners should protect caterpillars
Continue reading...I have always wondered: why are some fruits poisonous?
It was all the apple's fault: we've been fascinated by poisoned fruit for a long time. Jacob Jordaens (1593–1678), The Fall of Man, via Wikimedia CommonsThis is an article from I Have Always Wondered, a new series where readers send in questions they’d like an expert to answer. Send your question to alwayswondered@theconversation.edu.au
Why are some fruits poisonous when the objective of fruit is, presumably, to be eaten so that the seeds can be widely distributed with nutritive manure? – Sev Clarke, Mt Macedon
Poison fruit has captured our imaginations for centuries. Snow White’s death sleep was induced by the evil queen’s gift of a poison-laced apple. It is rumoured that deadly nightshade, a plant with naturally occurring fruit toxins, was used to kill a Roman emperor and halt an invasion of Scotland. A deadly dose of ricin from castor beans was administered to a Bulgarian dissident via the tip of an umbrella.
More recently, scientists have been trying to understand why some fruits are naturally poisonous. From the vain queen’s point of view it makes sense to poison an apple and feed it to the fairest in the land. But why do some plants offer poison fruit that has the potential to harm – or at least deter – fruit-eating animals?
Read more: Little shop of horrors: the Australian plants that can kill you
Fruiting plants and fruit-eating animals have “mutualistic relationships”, where each benefits from the other. Plants need to spread their seeds to colonise new territory, recolonise after disturbance, or avoid the dangers of staying at home (for example, if the parent plant harbours pests).
One way of doing this is to encase seeds in nutritious fruit pulp so that animals eat the fruit, digest the pulp, and later excrete the seeds with a helpful fertilising deposit of manure.
Animal-mediated (as opposed to wind- or water-mediated) seed dispersal can be particularly useful for getting seeds to specific locations. If you’ve ever wondered how parasitic mistletoe plants or strangler figs find their way onto branches high up in trees, fruit-eating birds are the answer. But why poison the pulp?
Birds spreading seeds are vital for many plants, so there has to be a very good reason to risk deterring them with toxic fruit.
Matt MacGillivray/Flickr, CC BY
Don’t you know that you’re toxic?
First, how do plants poison the pulp? Plants produce a range of chemical compounds, some of which have no apparent function in primary life-maintaining processes and so are called secondary compounds.
Potentially poisonous secondary compounds are produced either in the course of development from seed to adult plant, or in direct response to attacks from plant-eaters.
Poisons in fruit pulp are typically produced during development. Unripe fruit is often toxic to protect immature seeds from attack or premature dispersal, but ripe fruit with mature seeds can also be poisonous.
So how do we explain fruit that remains poisonous even when it’s ripe and ready for dispersal? One theory is that a low level of poison in fruit encourages fruit-eating animals to move away from the parent plant (avoiding additional poison), therefore carrying seeds further away.
In some cases toxins cause constipation, ensuring that seeds stay longer in the gut and so increasing the distance they are carried. In other cases – think of prunes – they act as laxatives to ensure the quick passage of seeds with minimal time for seed damage during digestion.
There is some evidence for these hypotheses, but they’re not the full story.
There’s good fruit-eating and bad fruit-eatingNot everything that eats fruit is good for the plant. Toxins in fruit might specifically target animals, microbes and fungi that damage its seeds, while being non-toxic to species that are good seed dispersers. The fruit of deadly nightshade is lethal to many mammals but apparently harmless to some birds, and Mediterranean buckthorn fruits are toxic to some insect pests but not seed-dispersing birds.
The fruit of deadly nightshade is poisonous to many mammals, but not the birds that carry its seeds.
Andreas Rockstein/Flickr, CC BY-SA
But poisons often discourage seed destroyers and dispersers alike, so plants face a trade-off between deterring assailants and attracting the animals that safely disperse their seeds. Research so far suggests that how plants balance this trade-off depends on how long they hold onto fruit.
Highly nutritious and attractive fruit is quickly found and eaten as soon as it’s ripe: think of a plum tree stripped by fruit bats in a night or two. These fruits face less risk of damage before they’re safely eaten by the right animals, so protective toxins are less important and are therefore produced in lower quantities.
On the other hand, plants with less nutritious fruit, rarer or unreliable seed-dispersers, or more predators need to protect their vulnerable seeds with toxic fruit.
Finally, fruit might be poisonous simply because the rest of the plant is toxic. This is another trade-off some plants make: toxins that protect leaves from herbivores can also end up in the fruit.
Recent research suggests that poison fruit may ultimately result from adaptation to a range of animals consuming different plant parts, so we need to consider the whole plant and its interactions with various organisms to understand the origin and function of poison fruit.
Understanding how and why plants produce poison, in their fruit or elsewhere, has led to discoveries that are valuable for reasons other than murder and mayhem. Naturally occurring plant poisons have been used for a range of medical purposes from painkillers to antimalarial and anti-cancer agents, and there are potentially many more useful plant poisons yet to be discovered in the wild.
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Julian MacPherson Brown does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.
Freedom for Miss Simpson, the penguin found 2,000km from home
A Snares penguin from islands south of New Zealand is found wounded on a Tasmanian beach. Nine months’ nursing later, she tastes the open sea again
Just before dawn on a still morning in autumn a crowd of people gathers on a beach in southern Tasmania. They watch in tense silence as a small animal shuffles across the sand. This animal, a penguin, has been the focus of nine months of care, liaison and cooperation to get to this moment – she is being released and sent back out into her world. I am privileged to be included in the farewell crew, and share the jubilation and anxiety of the people around me, all of us hoping that she will remember her path home.
ISS crew return to Earth
The eco guide to ocean waste
Plastic pollution in our seas is depressing – but there are imaginative moves afoot to address the problem
I’ve been sceptical about the power of running shoes to affect global change. So naturally I had it in for UltraBoost Uncaged Parley, Adidas trainers that claim to make peace with the ocean. The shoe’s upper is created from plastic waste retrieved from a clean-up operation in the Maldives, and recycled polyester. But Adidas has committed to producing a million pairs of these ocean waste running shoes, and a swimwear line.
Adidas has committed to producing a million pairs of ocean waste running shoes
Continue reading...Details of royalty deal for mega mine are still being negotiated with Adani, says Queensland
Palaszczuk government and mining giant apparently at odds as Adani says ‘there are no ongoing negotiations’ on Carmichael scheme
Queensland’s government says it is still negotiating with Adani over the details of its royalties agreement for its $16.5bn Carmichael mine, despite the deal being officially agreed months ago.
Adani announced in May it had reached agreement with the government over royalty payments, after a more generous offer of concessions was scrapped amid internal pressure from within the state Labor cabinet and caucus.
Continue reading...Cod and haddock go north due to warming UK seas, as foreign fish arrive
Our seafood diet must adapt, say scientists, as climate change forces some favourites to colder waters and threatens others
Britain must prepare itself for invasions of growing numbers of foreign sea creatures attracted by our warming waters, a new report has warned. Some newcomers could have devastating effects, others could be beneficial, say the researchers.
Examples provided by the team include slipper limpets that could destroy mussel and oyster beds. By contrast, new arrivals such as the American razor clam and Pacific oyster could become the bases of profitable industries for British fishermen.
Continue reading...Red legs flash over the green strand
Harlech, Gwynedd Redshank circle above Ynys while Roma samphire pickers search the saltings
A flight of redshank, wings elegantly barred and bent, clatter and yelp out of a draining channel as I circle Glastraeth, the “green strand” at the mouth of the river Dwyryd, which was once a crucial Welsh wintering ground for curlews, pintails and geese.
Related: Birdwatch: Common redshank
Continue reading...'Destructive wealth and arrogance': Bob Brown hits out at Adani group
Veteran conservationist compares situation to a nationwide action he led against the Franklin Dam in Tasmania in the 1980s
Veteran conservationist Bob Brown has criticised the “destructive wealth and arrogance” of Indian mining group Adani at a Sydney protest against the Galilee Basin mine.
The Adani chairman, Gautam Adani, announced this week that the company would break ground on it’s $16.5bn coal mine in Queensland in October.
Continue reading...The path to zero carbon energy
The path to zero carbon energy
North Queensland renewables boom
Country Breakfast Features Saturday 2nd September
A Big Country September 2, 2017
Multiple waterspouts spotted in Sochi
XFEL: Brilliant X-ray laser comes online
Floods, the Amazon at risk and the price of plastics – green news roundup
The week’s top environment news stories and green events. If you are not already receiving this roundup, sign up here to get the briefing delivered to your inbox
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