Too hot to handle?

floppy-claw-small

Although echidnas are pretty common, I’ve rarely seen seen them in Berowra.  So when I saw this one flopped out in the neighbours’ front yard on my sweaty walk home from work yesterday – ambient temperature in the mid 20s even at 7pm – I was worried.  Were echidnas, like fruit bats and stingless bees, troubled by temperature extremes?  Had this one been driven from its usual secluded haunts by this horrid heat wave?  Should I be on the blower to WIRES?

A cursory google did not inspire confidence.  Wikipedia notes that echidnas don’t sweat (in fact, they don’t pant, lick, or even wee on themselves and flap their wings to cool off either) and suggests that they “cannot deal with heat well“.  WIRES agrees that echidnas “cannot tolerate temperatures above 30 degrees“.

Notwithstanding, this seemed to be a very sprightly monotreme.  Most of the echidnas I’ve met have more or less fixed this position:

This beastie, however, was very busy, ignoring me and rummaging around in the flowerbeds.  Could it really be in trouble?  I decided, for the moment, that human intervention wasn’t necessary and then went home to check whether I’d just made a stupid decision.  Should I trust Wikipedia or my instincts?

I hit pay dirt when I found “Thermoregulation by Monotremes” by Queensland’s “Mr Hot Echidna”, Peter Brice.  As a researcher who has devoted time to  inserting “calibrated temperature sensitive radio-transmitters … coated with a smooth layer of inert wax… into the abdominal cavities of echidnas” (Brice et al 2002), he’s your go-to guy on this topic.

Niche subject as it might seem, the way echidnas and platypuses manage their body temperature has played an interesting role in propping up a hierarchical, human-centred view of evolution.  You’ve heard the story before, I’m sure. From this viewpoint, animals whose bodies are set up differently to us fancy-pants “classic mammals” are viewed as “primitive”.  Early twentieth century researchers decided that, for instance, that playpus had “an inadequate regulating mechanism” when after only 17 minutes at 35 degree temperatures, their research subject  “turned onto its back and fainted” (Brice, 2009, 260).  A poignant tale and the sort of thing that led one early twentieth century researcher to conclude that monotremes were “‘the lowest in the scale of warm-blooded animals’” (Brice, 2009, 256)

Don’t get me wrong, echidnas are very weird animals.  And that’s leaving aside the egg laying mammal business and the once-venomous spurs in their backwards facing hind legs.

Echidnas are cool. 31 degrees counts as a “normal” body temperature for them, though only females incubating eggs really keep their temperatures steady for long.  They seem to occupy a half-way house between warm blooded and “cold blooded” animals.  Echidnas don’t entirely rely on their surrounding environment to warm themselves as reptiles – ectotherms – do.  But unlike us humans – homeothermic endotherms – with our tedious need for a stable and predictable body temperature – echidnas can run hot or cold.

Just when you thought we were all “thermed”-out, you find that echidnas are also constitutional eurytherms – they can handle wide range of temperatures – and facultative endotherms – they warm their bodies up, in part, by doing stuff.

Echidnas also hibernate – well, some of them do, if they’ve eaten enough by the time the cold weather rolls in. But their hibernation, or its timing at least is, according to Brice (2009, 257) “distinctly odd”.  They often kip out during the late summer and then wake up to mate at coldest part of the year.  And they can deal with fluctuating temperatures in a way I can only envy – for instance, after a chilly night, they can dig their way out of shelter with their blood temperature of only twenty degrees.  With no bedsocks.

And they can also deal with a day spent in a hollow log at 40 degrees C without expiring from the heat, though no one knows exactly how.

We shouldn’t seeing echidnas and their wildly fluctuating temperatures as primitive, I reckon. Instead we should admire the way these critters harbour resources with their furry but weirdly chilly bodies, helping them live above the snowline in the Alps, in the desert and even on the sizzling streets of deepest surburbia.

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Echidna, close up and personal

References

Brice, Peter H. (2009) “Thermoregulation in monotremes: riddles in a mosaic” Australian Journal of Zoology, 2009, 57, 255–263

Brice, Peter H., Gordon C. Grigg, Lyn A. Beard, Janette A. Donovan (2002) “Heat tolerance of short-beaked echidnas (Tachyglossus aculeatus) in the field” Journal of Thermal Biology 27(6), 449-57

Happy Easter from Morgan the syncretic leghorn

We have pommie chooks!  Or from somewhere north of the equator, anyway.  I’m not sure how they managed to make the perilous transcontinental journey before their cute fluffy butts made it to our place at a week old, but somehow they must have dodged border control.

4 fluffy butts horizontal crop

How do I know our feathered friends come from the far north?

Well, here in Sydney, we’re past the equinox and the nights are drawing in.  We may have had a February that smashed heat records, 1.3 degrees C above the longterm averages.   But it’s hours of daylight that tells chickens when to get laying (thanks to that sort-of-third eye) and the days are getting shorter.  Even as the world goes to hell in a handbasket, it is, nonetheless, autumn.

And yet my chooks have decided to start laying.  Just in time for spring with its baby bunnies, and peeping chicks, and Easter eggs, and its celebration of rebirth and renewal.  In the northern hemisphere, that is.

I love Easter.  Most religious festivals are a delicious mish-mash of stuff from the Big Book and whatever else people were into at the time.  But with Easter the syncretism is really out there, bouncing around with its ears pricked up, laying  coloured eggs in the spring greenery.  After witnessing the pre-Good Friday panic by shoppers terrified by the prospect of a day without ready access to a new packet of Cocopops, the nice young guy at the checkout reckoned  we might add a zombie apocalypse to the usual combo of vernal equinox, Passover, and frenzied confectionary consumption.  As he pointed out delicately, Jesus did after all, come back from the dead.

In the midst of this cultural mash-up, it seems appropriate that it’s Morgan the flighty leghorn, named after a Welsh enchantress in an Arthurian legend, who has marked the occasion of the (deeply seasonally inappropriate) Christian festival of rebirth with the gift of her first lovely white eggs.

A muddled pagan blessing to egg eaters, one and all.

 

Broken Bay at low ebb

Last weekend I decided to explore the lower reaches of Mooney Mooney Creek from its meeting point with the Hawkesbury, riding on a rising tide. After my spooky solo paddles in Mangrove Creek, I had a hankering for the open horizon and a bit of human life around me. From my put-in at Deerubbin Reserve beside the freeway, and all the way round Spectacle Island, a nature reserve in the mouth of the creek, the constant hum of the traffic and the echoing rumble of trains crossing Brooklyn Bridge remind you that “civilisation” isn’t far away.

Low tide at Mooney Mooney Creek means mud and oyster leases.  The lingering blue haze from last week’s hazard reduction burns descended on the poles and frames, forlorn in the shallows, blurring them into beautiful abstracts.

The story of oyster farming in the Hawkesbury in recent times is a sad one, full of strange historical ironies.

People have been harvesting shellfish from the shores of the river for a very very long time and Sydney rock oyster has been farmed in Broken Bay since the 1880s.  In those days oysters were dredged from the estuary floor and after the meat was eaten, the shells, along with those from ancient middens, were burnt to make lime for mortar.

But in 2004, after a hundred years of farming oysters here, Qx disease hit the Hawkesbury.

The “Q” in the name stands for Queensland.  The Sunshine State produces a 10th of the oyster harvest it did in the nineteenth century, thanks to Qx and to the oyster-infesting mudworm (introduced from New Zealand in the 1880s along with imports of oyster spat). The “x” was a scientific shorthand for “what the hell is this anyway?  We really don’t know”.   Since then, researchers have figured out that Qx is caused by Marteilia sydneyi, a single-celled organism that during the summer infects oysters, causing them not just to slowly starve to death, but also to reabsorb their own gonads (nasty!).  The parasite then releases spores that cycle their way through a polychaete worm, Nephtys australiensis, in the winter, before reinfecting the oysters the following season.

M. sydneyi isn’t always the kiss of death.  The parasite is found in estuaries all along the coast of NSW and Queensland, even in “low risk” areas where Sydney rock oysters are still being commercially grown. Environmental stress, it seems, triggers outbreaks of Qx and surprisingly few wild Sydney rock oysters, the ones I saw lining the rocky shores of Mooney Mooney Creek, die from Qx. Which is good, if mysterious, news.

So, facing of losses of over 90% of the harvest, what could save the oyster industry in the Hawkesbury?

It was noxious pest to the rescue.

The Pacific oyster, farmed in Japan for centuries, was smuggled into Port Stephens in the eighties and spread quickly through the intertidal zones of New South Wales.  It’s a fecund and fast growing bivalve, planktonic eggs and larvae travelling far and wide, crowding, outgrowing, and sometimes settling on and smothering native rock oysters. A “selfish shellfish”, in the words of one inspired Tasmanian subeditor.

The very qualities that have made the Pacific oyster such a hateful invader came to the rescue of the Hawkesbury farmers in 2005.  A process for producing sterile “triploid” Pacific oysters had been developed in North America in the 1980s, with the aim of pumping out meatier shellfish fast. When fertility mean spawning 40 million eggs in a season (not to mention changing sex several times over a lifetime) avoiding reproduction saves a lot of energy.

Local farmers restocked with these “triploid” Pacific oysters.  As well as being immune to Qx, they were ready to harvest in less than two years compared to the three and a half years it takes rock oysters to reach the table.  The new “tamed” Pacific oysters took the Hawkesbury by storm.

And then in 2013 disease struck again. Millions of oysters were wiped out overnight by a virus that affected Pacific oysters and Pacific oysters alone.

Like the oyster itself, the scientifically spawned sterile “triploids”, and indeed the settlers that farm them, “oyster herpes” or POMS (Pacific Oyster Mortality Syndrome), first seen in France in the late noughties, had circled the globe to Broken Bay.

Only three oyster farming businesses are still going in the Hawkesbury these days, hanging on for scant supplies of Qx resistant rock oyster spat, first found amongst the survivors of the Georges’ River outbreak in the mid 1990s.

Right now, the derelict oyster farms are mostly places for posses of pied cormorants to hang out.

But there’s still plenty of life to be found at Mooney Mooney at low water: globe trotters like the eastern curlew, exhausted after a long flight south, and locals like the rock warbler that only lives on Sydney sandstone, compensating for its drab colours and homebody ways with a goth-style nest of grass and spider webs it hangs in the darkness of caves and crevices. And I clocked a new heron record – twenty at least, catching crabs in the mud of low tide.

References

Michael C Dove, John A Nell, Stephen Mcorrie and Wayne A O’Connor “Assessment of Qx and Winter Mortality Disease Resistance of Mass Selected Sydney Rock Oysters” Journal of Shellfish Research 32(3) 681-87 doi: http://dx.doi.org/10.2983/035.032.0309

Wayne A O’Connor and Michael C Dove “The changing face of Oyster Culture in New South Wales, Australia” Journal of Shellfish Research, Vol. 28, No. 4, 803–811, 2009.

J.A. Nell “The history of oyster farming in Australia” Marine Fisheries Review 63(3), 14-25

Autumn in terminal decline?

In amongst the nasty consequences of global warming – sea-level-rise-ocean-acidification-violent-storms-heat-waves-large-scale-extinctions (if you say it quickly and rock back and forth at the same time it doesn’t seem quite so bad) – a decline in the intensity of autumn leaf colour really doesn’t draw the eye.  Bar a few unusual plants like the red-fruited kurrajong and the Antarctic beech, most deciduous plants around here aren’t even natives.  So who cares, eh?

But as I huddle in my chilly house on its shady south-facing hillside, waiting for the leaves on the neighbour’s looming liquidambar to fall, the impact of climate change on deciduous trees seems like a tremendously pressing question.

I’m not the only one gripped by this crucial topic.  The latest  Trends in Ecology and Evolution has roundly denounced the scandalous neglect of autumn. Spring gets its own live feed on BBC TV, but even scientists get depressed by extended discussions of leaf senescence, it seems.   Garnering less than half as many articles as its greener sibling, autumn, according to the indignant authors, is a “neglected season in climate change research”.

Well, neglected no longer!  Not here in the backyards of Berowra.  Right here, right now we bring you…. in the prophetic words of Gallinat and her outraged colleagues… “the future of autumn research”.

As we march boldly into fall’s future, I’m cling to the hope that photoperiod (that’s the day-length to you and me) will rescue me from climate change, sending that winter-sun-blocking foliage promptly into the compost bin regardless of how roasting hot it is. And it’s not a vain hope – the amount of light a deciduous plant receives does seem to help many decide whether it’s time to shed their leaves or not.

In the case of liquidambar, long days or lots of light delay dormancy, as you can see from these nifty pictures of a specimen down the street, well illuminated day and night so as to minimise deaths on a local pedestrian crossing, clinging to its leaves long after its neighbours have shrugged their own.

Depressingly, it does seem that sweetgums need cooler weather to finally ditch their leaves, even in the short days of midwinter.   Photoperiod matters most near the poles – but for trees at the lower latitudes (like Sydney, curse it) temperature is the clincher.

This raises interesting questions about the future of the veggie garden. Around the winter solstice it lurks in the shade of our dawn redwood, a living fossil that grew across the temperate Arctic when dinosaurs stomped the earth, and was dramatically rediscovered in the 1940s in a single isolated valley in China.  Will its gorgeous copper needles still fall in time to give my broadbeans a decent run-up to spring when we’re wearing shorts all winter?

In the words of a Facebook status update, “it’s complicated”.  Could this be why climate scientists, like nervous singles, are staying well clear?

For instance, warmer springs lead to earlier bud burst, which can sometimes mean earlier leaf-fall.  And deciduous trees in general tend to lose their leaves more readily in dry weather.  “On average”, according to Estiarte and Peñuelas (2015) “climatic warming will delay and drought will advance leaf senescence”.  Work that one out.

And that’s not even throwing nutrient availability into the mix.  For instance, what if trees start going ballistic with all that carbon dioxide in the atmosphere?  This vision of a greenhouse planet jungle awash with joyful plants growing at breakneck speed sounds like something out of a climate denialist fantasy, doesn’t it?  “More open cut mines, pretty please!” beg the earth’s desperate forests “my future is coal!”

Sadly for the wind-farm haters, it mostly doesn’t work like that.  Carbon dioxide can give trees a flying start but eventually the nitrogen supply conks out, or drought and too much CO2 do the leaves in.  Even with the help of globe-trotting survivors like sweet gums and dawn redwoods, coal (and copious quantities of greenhouse gases) won’t make the world greener.  Let’s just hope, even gardening in our bikinis, we can still find gold.

References

  1. Estiarte, M and Peñuelas, J (2015) “Alteration of the phenology of leaf senescence and fall in winter deciduous species by climate change: effects on nutrient proficiency” from Global Change Biology 21(2) 1005-17
  2. Flexas, J, Loreto, F and Medrano, H. (2012) Terrestrial photosynthesis in a changing environment: a molecular, physiological and ecological approach, Cambridge, Cambridge University Press
  3. Gallinat, AS, Primack, RB, Wagner, DL (2015) “Autumn, the neglected season in climate change research” from Trends in ecology and evolution 30(3)
  4. Warren JM, Jensen AM, Medlyn BE, Norby RJ, Tissue DT, (2015) ‘Carbon dioxide stimulation of photosynthesis in Liquidambar styraciflua is not sustained during a 12-year field experiment’, AOB Plants, vol.7, Article no.plu074
  5. Warren, JM, Norby, RJ, Wullschleger SD (2011) ‘Elevated CO2 enhances leaf senescence during extreme drought in a temperate forest”.  Tree Physiology 31, 117-30
  6. Worrall, J (1993) “Temperature effects on bud-burst and leaf-fall in subalpine larch” Journal of Sustainable Forestry 1(2)

Low tide at Gunyah Beach

“The sea or not the sea?”

That was the question churning through my brain, as I set out for my first solo kayak on the Hawkesbury proper.  Let’s be kind and say I’m not a risk taker (there’s a reason I’m fond of chickens).  And my canoe is properly vintage, made out of wafer-thin plywood back in the early 70s, and now held together by a rich tapestry of epoxy based products and amateurishly applied fibreglass.  Don’t get me wrong – it was the best $100 I ever spent on ebay but our Egg is no ocean-going liner.

But setting off on a sunny Saturday morning with a light off-shore wind and a slack tide, I thought my decrepit boat and I might just be able to brave a three kilometre paddle along the widest reaches of the Hawkesbury Estuary, from Brooklyn’s Parsley Bay to Gunyah Beach in Kuring-gai Chase national park.

About midway across the 700 metres at the mouth of Porto Bay, I realised the weird rise and fall of the boat was swell, a new and disturbing experience for me as a canoeist.  Well, it was either swell or the kayak was being regularly nudged sideways by bull sharks.  Either way, I was not happy.   It didn’t help that the choppy water was full of floating branches, torn down by  last week’s big winds.  If the sharks didn’t get me, I’d be turned into a giant vegetarian shishkebab by a surfing pine tree.  I was in the ocean, and it was scary.

Of course, the Hawkesbury “River” is, kinda, the sea – a flooded river valley that has its tidal limit a hundred kilometres or thereabouts from its mouth.  Whenever I think about this, I imagine how strange it must have been for the people living on the plains that once stretched out from the current coastline under what is now the surface of the sea, as the ocean crept slowly up, over ten thousand years, claiming the valleys carved out by the river, pushing people before it into the hills.  Now that’s really going into the unknown.

In the end, of course, I made my little paddle with no problems at all, apart from an annoying lack of photographic evidence that there was ever anything to fear.  Gunyah Beach (boat access only) even had its own lounge suite on which an unnerved canoeist might rest and recover.  I’m pretty sure the contractual obligation white-faced heron had just stood up after a cup of tea and a chocolate digestive as I arrived.

Stumbling through the mud around the beach-side lagoon, I found myself in a maelstrom of silvereyes and white cheeked honeyeaters.  I’ve come to realise binaural hearing is a real asset for bird watching.  With one dodgy cochlea I spent half my time whipping my head wildly from one side to the other to work out where the chirping was coming from.  In the end taking random pictures of the bushes seemed the best way to avoid permanent neck injury. I was disproportionately pleased with the few photos that worked out. There’s something particularly delightful about the most minor victories over timidity and incompetence, even if you can’t convincingly frame pootling around in boats in your estuarine backyard as some kind of heroic feminist re-enactment of The Old Man and the Sea.

Timber!

We’ve had a mob of at least fifteen yellow tailed black cockatoos hanging around in the last few days, mewing like strangled cats and being chased around by magpies and (I think) even noisy minors.  We get the yellow tails quite often around these parts, especially in the winter-time, thanks to the large and sickly but apparently tasty radiata pines that loom over our place.

The rule in Hornsby Shire is you can cut down a tree that’s within three metres of the foundations of your house.  If only there was some special by-law where the council chops down the tree for you for free if you can’t slip a paperback book between a towering pine and your bathroom.  One of these days I’ll be communing with nature and the nearest treebole will swell just that tiny bit further and burst straight through into the shower cubicle. That fresh piney smell with not a cent spent on disinfectant.

It’s been very very very windy in Sydney lately, and quite a few people have been unfortunate enough to experience that piney odour, quickly followed by plenty of refreshing indoor rain. We’ve been pretty lucky, but we’ve spent a lot of time staring anxiously out the window at various ominously swaying monumental specimens.  When I lived in Brisbane I used to be a bit judgey about the lawn to tree ratio in most peoples’ yards.  But if cyclones start creeping their way down the coast I may have to reconsider.

Yellow tailed black cockatoos are doing pretty well on the east coast, including urban areas, no doubt thanks to their penchant for pines.  But apparently they often struggle to find nesting sites, preferring hollows in trees a century or more old.  They seem to like our senescent radiatas, and spend time perched high on the various dead branches voguing.  I hope, when we finally save enough shekels to pull down the extensive array of dangerous trees in our yard, we still see them.

Maps in bloom

Perhaps I’ve simply been oblivious before, but this year it seems the bush around Berowra is awash with flowers –  white posies crowning the Sydney red gums (Angophora costata) that now appear to be on every street corner, ridgetop and slope.

There’s something strange about this foam of blossom appearing across our familiar view, as if, while we weren’t looking, a stagehand unrolled a new backdrop to our lives.  I’ve become a tiny bit obsessed by capturing this new scene on camera. Here’s a small sample of my multiples.  Andy Warhol eat your heart out.

Closer to town, the jacarandas are also out.  I love the way this royal bloom redrafts the map of the suburbs, rerouting your eye from the usual lines of roads and railways and wires, to a new dot-to-dot of superbly laden trees.  The city shifts on its axis.  Or better, the city’s axis, the radial city itself, retreats behind a mist of purple flowers.
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Of course, this new cartography of living things is still a map of privilege, of the breathing space between people.  They don’t call affluent parts of town “the leafy suburbs” for nothing.

Creating and keeping green space gets more urgent as cities get hotterAn article in the Harvard Gazette reports research on the way inequality, heat and green space correlate.  “Heat” says Joyce Klein Rosenthal, who teaches in Harvard’s School of Design, “is an environmental stressor, unevenly distributed in places where there are less trees, less green space, and associated with poorer housing quality”.   “At every scale” she noted “income levels are associated with surface temperatures. Poorer neighborhoods are hotter; wealthier neighborhoods are cooler”

Street trees have magic carpets beneath them, not just lilac flowers, but shade.  And on a stifling day the breath of wind across a city park – old-school evaporative airconditioning – is almost as good as the breeze off the water.  Just now, the City of Sydney is trying to green streets and villages, beating the urban heat island effect by shading concrete, weaving plants into walls and sowing seeds on roofs.

But, that hasn’t stopped the chainsaws round here.  New regulations in NSW, created in the name of fire risk-management, let householders rip, at least on trees ten metres or less from their place (oddly, it seems that trees in the middle of spectacular views present the greatest fire hazard).  What an irony: climate change, worsened by tree-felling, makes the Australian weather hotter and extends the bushfire season.  We fear the urban forests, just as we need them the most.

After years of cultivating a back yard the size of a large picnic blanket (that’s to say, a picnic blanket made of concrete) every day I bless the growing things I see from my window.  I may feel differently one day when the view from my back deck is Sydney red gums topped with flame rather than flowers.  Let’s hope I don’t find out anytime soon.