pollination

Fur and Flowers: Melbourne's Mammalian Pollinators

This is a guest post by Mackenzie Kwak.

These days there’s a lot of buzz surrounding pollinators. When most of us think of them, our minds quickly turn to bees and butterflies. However, in Australia we have a diverse range of warm-blooded pollinators working through the night to keep our forests growing strong, and many of them call our city home.

Ancient Australia

Australia is a global hot spot for mammal pollinators. To better understand the close relationships between these warm-blooded creatures and their floral friends, we must turn our minds back millions of years to prehistoric Australia when flowers first appeared on the continent. For a very long time before the present day, Australia sat much farther south and at one point even stood where Antarctica now rests. At that time though, the globe was much warmer and plants could survive on this cool, southern continent known as Gondwana. Although polar forests flourished, temperatures still remained low, especially in winter when the forests often froze over. This provided a real challenge for plants eager to be pollinated.

Brushtail possums are one of the most common mammalian pollinators encountered around Melbourne.  Image: Wikimedia Commons

Brushtail possums are one of the most common mammalian pollinators encountered around Melbourne. Image: Wikimedia Commons

Insect pollinators were not common in Gondwana at this time due to one basic problem with their biology: cold blood. Insects are commonly described as cold-blooded or more accurately poikilothermic, meaning their body temperature fluctuates with the ambient temperature. However, insect body temperature can fluctuate so much that sometimes it rises far above that of mammals and birds,  making the term ‘cold-blooded’ a little erroneous. Fluctuating body temperature creates some major difficulties for insect pollinators - especially when the ambient temperature is close to freezing and pollination activity becomes impossible. It was these cool conditions that gave mammals their first real go at pollination in Australia. Mammals are warm-blooded, or, more technically, homeothermic, and can control their internal temperature even when the ambient temperature majorly fluctuates. This means that they remain active at much lower temperatures than their six-legged competitors and can exploit the rich nectar resources that plants have to offer. Over time, many mammals specialised to feed on this rich food and plants in turn modified their flowers to attract warm-blooded pollinators. 

Possums

Ringtail possums are another extremely common possum species of Melbourne.  Image: Emma Walsh

Ringtail possums are another extremely common possum species of Melbourne. Image: Emma Walsh

Possums are perhaps the most commonly encountered native mammals in the greater Melbourne region. Most folks view them with a strange combination of weak interest and mild irritation because of their all too common habit of taking up residency in our roofs. Possums, though, are important pollinators of many native trees and shrubs throughout Australia. We are most familiar with the common brushtail possum (Trichosurus vulpecula) and common ringtail possum (Pseudocheirus peregrinus) that are regular visitors to the flowers of gum trees. But while these two species supplement their diets of leaves with whole flowers, nectar and pollen, the real heavy lifters among the pollinating possums are the gliders.

In the greater Melbourne region the most common of these is the sugar glider (Petaurus breviceps), which incorporates a huge amount of pollen and nectar into its diet along with insects and tree sap. These little possums live in family groups, reside in tree hollows, and are important pollinators of Eucalyptus trees. Melbourne is also home to the world’s smallest glider, the feathertail glider (Acrobates pygmaeus), which weighs about 14 grams and is small enough to fit in the palm of your hand. While these little possums are far from common, they can still be found in the forests near Frankston and in Melbourne’s north-east. Like the sugar glider, they are also voracious pollen feeders but supplement their diet with insects.  

It's no secret why we call this little possum species the feathertail glider!  Image: Wikimedia Commons

It's no secret why we call this little possum species the feathertail glider! Image: Wikimedia Commons

Bats

Bats are another group of mammal pollinators often viewed with some antipathy by the general public because of their noisiness and propensity towards raiding fruit trees. However, bats are much more important to Australia’s ecosystems than many people realise. It’s important to note that the majority of bats that call Melbourne home do not act as pollinators - these are the microbats and they are in fact carnivores or insectivores. The grey-headed flying fox (Pteropus poliocephalus) is Melbourne’s only bat pollinator and reaches sizes far greater than its small carnivorous relatives, with wingspans up to one metre. Grey-headed flying foxes feed on a range of different flowers throughout the year but particularly favour the Myrtaceae family which includes the eucalypts, honey myrtles and tea trees, as well as the Proteaceae which includes the banksias and grevilleas. Fruit bats are not only important pollinators, but also critical seed dispersers for many native plants as well.

Dasyurids

Perhaps the strangest mammal pollinators to call the Melbourne region home are the Dasyurids, a group which few people have even heard of let alone considered as pollinators. For those unfamiliar with the often complex world of mammal taxonomy, the Dasyuridae is a family of mammals that includes quolls, Tasmanian devils, the now extinct Tasmanian tiger, and a range of other small, carnivorous marsupials. Many small Dasyurids resemble rodents superficially, but all possess a pouch which sets them apart. The genus Antechinus is one of these rodent-like groups of marsupials and Melbourne is home to three species: the swamp antechinus (Antechinus minimus), dusky antechinus (Antechinus swainsonii) and agile antechinus (Antechinus agilis). In other parts of Australia, Antechinus species are known as excellent pollinators of Banksia sp. but it remains unclear what role our Melburnian species may play in the pollination of local flora.

The agile antechinus is one of three  Antechinus  species to call Melbourne home.  Image: Wikimedia Commons

The agile antechinus is one of three Antechinus species to call Melbourne home. Image: Wikimedia Commons

It is not yet clear what role Melbourne's  Antechinus  species play in pollination.  Image: Wikimedia Commons

It is not yet clear what role Melbourne's Antechinus species play in pollination. Image: Wikimedia Commons

One Melbourne resident known to be a good pollinator is the brush-tailed phascogale, which resembles a squirrel but is actually a nocturnal, carnivorous marsupial. These secretive little mammals have been recorded gorging themselves on nectar and pollinating flowers with masses of pollen adhering to their furry muzzles. However, like many of our shy native marsupials, it is believed that the brush-tailed phascogale is sadly declining around the Melbourne region due to habitat loss.

So next time you see fruit bats glide overhead or hear a possum scurry across your roof, just remember the surprising task that these pollinators undertake. Although they may not be as glamorous or well-liked as native bees or butterflies, mammals are key pollinators of many of our native plants. It's now our responsibility to halt their decline, as losing them could be catastrophic. 


Mackenzie Kwak is a zoologist with a broad interest in Australia's diverse flora and fauna. His research focuses on the biogeography, systematics and ecology of Australasian ectoparasites, particularly ticks, fleas and lice. 

Banner image of a grey-headed flying fox courtesy of Wikimedia Commons.

To Bee Or Not To Bee

I love the end of winter. It’s as though, just when the icy mornings seem like they’ll never end, native flowers burst out and practically sing at us that the wait is over and we’re heading into spring. Wattle bursts out bright and golden all over the place. Brilliant red banksias droop down to the ground, surrounded by pale green leaves. Buzzing bees flit between flowers, wiggling their bright blue bums as they forage for nectar.

…Wait a minute…

If, like me, when someone says bee you mentally picture something like this:

…then the thought of a bee with a blue bum may be a bit surprising. Bees are yellow, right? Black and yellow, to be more specific. What’s more iconic in the bee world than the image of the yellow, fuzzy honeybee Apis mellifera? As iconic as this image is, it turns out that it only became part of the Australian landscape as recently as 190 years ago, and clearly didn’t get here on its own! The European honeybee (Apis mellifera) was introduced to provide a reliable source of honey for colonisers. The fact that they even survived the journey is pretty impressive – after all, there are notoriously few flowers in the ocean! While early Europeans may not have intended for bees to escape into the environment, inevitably it happened. Decades later, they’ve made themselves at home across virtually the entire continent. Managed hives of European honeybees continue to pollinate many of Australia’s crops, and the value of pollination and honey services from these hives is estimated to be in the billions.

As well as our crops, European honeybees visit our native plants. This results in some pretty delicious (and uniquely Australian) honey flavours, but it begs the question, what is the impact of these bees on our native pollinators?

Australia has an amazing diversity of bees, with over 1,500 species of native bees. In northern, tropical regions of the country, social species of stingless bees are commercially sold as pollinators and honey producers. However, the majority of our native species are peaceful, solitary creatures, with a variety of interesting behaviours.

Victoria is home to seven of the ten major groups of native bees – reed bees, blue-banded bees, teddy bear bees, leafcutter bees, resin bees, masked bees, and Homalictus bees. The behaviour of these groups is incredibly diverse. For example, the small but beautiful Homalictus bees have large, intricate branching nests, some of which house many females that all take turns guarding the nests from intruders. Those familiar with leafcutter ants may have a clue as to the behaviour of leafcutter bees, which cut disks out of leaves and use them to build their nests.

My personal favourite, resin bees collect resins and gums for their brood cells and nest holes, and on occasion may try to ‘borrow’ some resin from the nests of stingless bees. Some of these species are dazzlingly beautiful, with species of Homalictus bees ranging from golden-blue to coppery red. Others, such as masked bees and reed bees, are mainly black in colour, with only a few bright markings. One of the most dynamic of the bee groups, the blue-banded bees are delightfully rotund and have bright stripes of white or blue across their abdomens.

The alluring blue-banded bee ( Amegilla cingulata ). 

The alluring blue-banded bee (Amegilla cingulata). 

There has been a dramatic increase in the number of feral European honeybees in the last 80 years. As many of our native pollinating species have considerable environmental overlap with European honeybees, this spread could indicate considerable trouble for our natives. There has been a number of investigations analysing potential impacts of European honeybees; however, a review by Paini (2004) found that most of these studies suffered from confounding factors or low replication, making it difficult to ascertain how much of an impact invasive honeybees are directly having on native pollinators. As recently as 1992, the bumblebee species Bombus terrestris has inhabited Tasmania, spreading widely across the state in the short time it’s been there. While there is some evidence of displacement of native bees, the major concern is how B. terrestris increases seed production of invasive weeds, helping them to disperse further.

This seems to be the issue on the mainland as well: European honeybees are also fond of non-native plants like Scotch broom, resulting in a decrease in native flora and feeding opportunities for our native bees and pollinators. While the impact of invasive bee species may still be unclear, what researchers generally agree upon is that deforestation and loss of floral and nesting resources is one of the major concerns for our native bees. Clearing of land for agricultural use decreases their available habitats, whilst constant grazing can restrict the regeneration of particular plants, restricting their range.

All of this raises the question: how can we ensure our native bee species are preserved so that we don’t lose them forever, as has been seen in parts of Europe? One answer may be in commercial applications. For example, the blue-banded bee is currently being investigated as a potential pollinator for tomato plants, thereby eliminating the need for B. terrestris on the mainland. Another avenue is an increase in public interest. In the UK, the Bumblebee Trust has taken off in recent years, as the public became aware of their decreasing numbers and sought to save the species that remained.

In the last decade, the persistence of the drought has led to a push for Australians to plant native species in our gardens. Appreciation for our native flora has been slowly and steadily increasing. Combining this with an awareness for our native bee species could be a way of encouraging public engagement and enthusiasm for our natives, and ensuring their survival as factors such as climate change become increasingly unavoidable. 

After all, who wouldn’t want to save our bright blue beauty? 

For more information on Australia's native bees, refer to Tim Heard's book on the topic and this article about their conservation.  


Mary Shuttleworth

Mary Shuttleworth is a Masters graduate from the University of Melbourne, where she pursued her interests in ecology and parasitology. She is interested in science communication, education and community engagement.

Find her on Twitter at @muttersworth.


Banner image courtesy of http://www.bellingenbees.org.au

Environmental Accounting: The Way Forward?

This piece is co-authored by Rachel Fetherston & Billy Geary

As people who are somewhat environmentally concerned, we are constantly asking ourselves one question: how do we best communicate the importance of nature to those who we have elected to make decisions for us?

Sure, we can pull out statistics like “Australia has the worst mammalian extinction rate on Earth”, or “there are only 50 to 60 orange bellied parrots left in the world.” But is this negative 'you-better-do something-or-else' mantra working? It certainly doesn’t seem so.

There aren't many mammals left in this eucalyptus forest, but is that a useful message to convey when trying to engage people in conservation? Sherbrooke Forest, Victoria. Photo: Robert Geary

There aren't many mammals left in this eucalyptus forest, but is that a useful message to convey when trying to engage people in conservation? Sherbrooke Forest, Victoria. Photo: Robert Geary

Often with nature blogs, we’re preaching to the converted. You’re probably thinking to yourself right now: “What can I do to help reverse the current situation?” On the other hand, we might get the inevitable response from Joe Bloggs in the street: “Why should we save something that does nothing for me?” It’s a fair point. Aside from its intrinsic value (i.e. taking value from the simple knowledge that things exist), what exactly does the orange-bellied parrot do for the average person?


Money Matters

The world revolves around money - this we know for sure. In the age of free markets and gross domestic products, most governments are almost solely focused on achieving a surplus. Unfortunately, the environment rarely gets considered in such conversations, aside from the occasions it becomes a resource (i.e. timber harvesting, redirecting stream flows for irrigation). One approach to resolve this is to put a price on nature, a process called environmental accounting.


Environmental accounts

The approach to environmental accounting is simple. By applying accounting principles to quantifiable aspects of nature, we can estimate how much a species, ecosystem or region is worth to the economy and therefore measure how its worth changes over time. The significance of this is substantial, potentially allowing for the importance of nature to be communicated beyond its intrinsic value.

In fact, the Wentworth Group of Concerned Scientists (including acclaimed scientist Tim Flannery) has highlighted developing a set of environmental accounts as an important step in the conservation of Australia’s biodiversity. Why? Because money is the language of human civilization. If we can quantify nature in terms of dollars and cents, we are suddenly speaking the language of those in power; those who make the big decisions and run the world. Essentially, we would be illustrating the value of nature in the most literal way that is currently possible.  

Furthermore, if we can put a dollar-value on entire ecosystems, we can then measure how their value might change over time. This allows us to monitor how our actions, good or bad, impact the environment on a large scale. This is inherently relatable to other businesses and industries that measure success or failure in terms of money.

Is this alpine woodland worth more to society for its intrinsic value or for the tourist dollars it brings in? Lake Mountain, Victoria. Photo: Robert Geary

Is this alpine woodland worth more to society for its intrinsic value or for the tourist dollars it brings in? Lake Mountain, Victoria. Photo: Robert Geary


Natural Capital: How much is that wetland worth?

For years now, various groups have attempted to put a price on nature. The seminal but controversial paper by Daily et al (1997) estimated that the Earth and its ecosystems could be valued at a whopping $127.3 trillion. This process essentially asked the question: “How much money would humans have to spend to ensure ecosystem function and services are maintained in the event nature stopped doing it for us?”

One way to look at it is to think of a local wetland or creek and the complex things it does. A stream might flow through it, and the plants, algae and invertebrates all contribute to cleaning and filtering its water. This could even be a tributary that runs into the Thomson Dam, Melbourne’s largest source of drinking water. Taking away the naturally occurring water filtration system, humans would have to perform that same function to ensure we could still drink water from the dam. That, as you can imagine, would cost big bucks.

Radiolab's story on the value of nature begins at 51:50. 

This concept has actually been put into practice with another incredibly important and valuable process: pollination. A recent study put the value of crop pollination by bees, bats and birds to the American economy at $29 billion. This is an enormous figure, illustrating that if pollination stopped, so would the American economy to a major extent.

This has actually happened in China, where mass die-offs of pollinators (e.g bees) led to Chinese farmers having to pollinate each crop by hand. As reported by Radiolab, this led to an increase in profits because the minimum wage is so low in China. However, in a developed country, pollination by hand would bear an enormous cost to the economy.


Problems: The Worth of Pricelessness

There is an inherent problem with the environmental accounting approach. How does one put a price tag on that which is priceless? Inevitably, there are some things that, comparatively, aren’t worth anything to humanity in terms of dollars and cents. For example, should we place the same monetary value on species that differ in terms of their influence on ecological function?

Consider comparing the value of a rare keystone species such as a large predator to that of a small rodent which shares an ecosystem with species that are ecologically similar. The former would perhaps be considered much more ecologically ‘valuable’ than the latter whose function can be carried out by a number of other organisms.

How much are unique apex predators, such as the grey wolf ( Canis lupus),  worth to ecosystems?  Photo:  Malene Thyssen  ( Wikimedia Commons )

How much are unique apex predators, such as the grey wolf (Canis lupus), worth to ecosystems?

Photo: Malene Thyssen (Wikimedia Commons)

What about the agile antechinus ( Antechinus agilis ) which is often found where other species of antechinus and rodents occur?   Photo: Mel Williams ( Wikimedia Commons )

What about the agile antechinus (Antechinus agilis) which is often found where other species of antechinus and rodents occur?  
Photo: Mel Williams (Wikimedia Commons)

This intrinsic value of nature and its relative importance in comparison to monetary value is a key tension. This must not be forgotten when considering environmental accounts as a tool, lest we risk ignoring those aspects of nature that do not provide a ‘service.’

The problem here is that ecologically non-significant species would suffer in the context of environmental accounts. For example, many of Australia’s increasingly rare species could be deemed economically irrelevant in terms of ecological function and would subsequently be last on the priority list when it comes to ‘valuing’ our natural world. There would indeed be casualties, as there are in any budget. 

Such a view of nature is therefore perhaps part of the problem. Viewing our natural world through the human eye means that we more highly value what is useful to us, but value less that which may actually be vital to the non-human.

Many environmental philosophers explore this concept, deeming such a view an ‘anthropocentric’ understanding of the world around us. Unfortunately, opposing anthropocentrism also involves opposing the primary idea at the root of environmental accounting – that is, capitalism. Should we be placing a dollar-value on nature or should we be learning to value nature more than the dollar?

In the opinion of many leading environmental philosophers and ecocritics, the capitalist model of the West is becoming more and more unsustainable in the face of climate change and environmental destruction. Amongst others, Val Plumwood is one philosopher who suggested that people still struggle to perceive the natural world without the influence of human bias.

The term ‘non-anthropocentrism’ is often used to describe a worldview that attempts to encompass a less human-centric appraisal of nature. This would involve a society that deprioritises monetary gain and instead accepts that humankind’s understanding of nature does not and often cannot involve the needs of the non-human.

That is not to say that it would be easy to implement said non-anthropocentrism. In many ways, it is currently an impossible as well as undesirable prospect. In the context of such a radically different worldview, humans may no longer enjoy many of the positive features of a society that values material goods and services; our favourite movies and TV shows, the amazing variety of products that some are lucky enough to afford, and perhaps even the ability to take a holiday and visit some of our world’s incredible natural wonders are just some of the things that may be lost if we choose to devalue financial gain.

For all of humanity's impacts on it, it is still the intrinsic value of nature that draws us in - each and every time. Lake Mountain, Victoria. Photo: Robert Geary

For all of humanity's impacts on it, it is still the intrinsic value of nature that draws us in - each and every time. Lake Mountain, Victoria. Photo: Robert Geary


Can we have our cake and eat it too?

The bigger issue is, then, is it possible to have our cake and eat it too? Can we enjoy the perks of placing a monetary value on the environment whilst simultaneously educating the public to understand nature through a ‘more-than-human’ lens? It is a difficult thing to test, but is indeed something to keep in mind if a monetary model for nature is developed.   

So, is environmental accounting a silver bullet for speaking the language of politicians and treasurers across the world? No, not really. But, it does help us further communicate the value of nature to those that cannot or will not connect with its intrinsic value. Thus, it has the potential to be a very, very useful tool for ensuring the environment gets a seat at the budget table – something that has scarcely occurred in recent times.