On today’s show we learn about the Brown’s Banksia, a critically endangered flowering shrub native to southwestern Australia, about 200 miles south of Perth in the state of Western Australia.
For more information about Brown’s Banksia conservation please see the Australian government’s Department of Climate Change, Energy, the Environment and Water - https://www.dcceew.gov.au
Rough Transcript
Intro 00:05
Welcome to Bad at Goodbyes.
On today’s show we consider the Brown’s Banksia.
Species Information 02:05
The Brown’s Banksia is a critically endangered flowering shrub native to southwestern Australia, about 200 miles south of Perth in the state of Western Australia. Its scientific name is Banksia brownii and it was first described in 1830.
Description
The Brown’s Banksia is a medium to large shrub, that on the windswept peaks of its habitat, grows low and bushy ranging from 3 to 10 feet in height. Though some individuals, of the same species, found in more sheltered valleys and ravines, develop into a more open branching small tree, reaching up to 20 feet in height.
Botanists will describe plants using familiar terms like “tree,” or “shrub,” or “bush” which are super useful to get a quick idea of what a plant may look like, but these are not like formal scientific classifications. For example there is no universal consensus on how tall a plant must be, to be considered a tree, not a shrub. And there is a lot of perhaps intentional ambiguity in these descriptors, because, as we see with our Banksia, a plant’s environment can significantly influence its growth form. Hard delineations may in fact confuse species identification.
So then, the Brown’s Banksia is a woody perennial (it has wood stems and branches, and has a multiple year lifecycle of growth and dormancy) which can develop a shrub-like growth form and appearance, or a tree-like growth form and appearance based on environment and growing condition.
It is sometimes referred to as the Feather-leaved Banksia because each leaf is divided into as many as 70 thin, slightly curved lobes, creating a soft delicate, feather-like appearance. The top side of the leaves, the adaxial side are dark green, and the bottom the abaxial side are light green, covered in fine white hairs.
These hairs are called trichomes, and they help prevent water loss by trapping a thin layer of humid air right against the surface of the leaf which slows down the rate of evaporation, helping the plant conserve water.
Trichomes are also a physical barrier to deter grazing by small, leaf-eating insects; simply making it more difficult to walk on the leaf surface and to feed on the leaf itself. You get a mouthful of hair.
The Brown’s Banksia leaves are long and narrow, measuring up to roughly 5 inches in length and a quarter inch wide.
Its bark is smooth, brown-ish grey, and marked with lenticels, small pores that aid in plant respiration, breathing.
The Brown’s Banksia’s flower is unusual and striking. It grows from the ends of the stems in a cylindrical “flower spike” growth form. In the literature I reviewed, this flower form is frequently described as looking like a ‘bottlebrush’. If you are anything like me, not born in the 1800s, and have no idea what a bottle brush looks like a less poetical but perhaps more evocative image is, it looks like a toilet-brush. But like the prettiest toilet brush you’ve even seen.
Reproduction
The flower spike is about 6 inches in height and 3 inches in diameter with a bristly appearance. It’s a cluster, an inflorescence, of hundreds of individual flowers spiraling around the stem. Each individual flower has a tiny thin, long, wiry, style (that’s the female pollen receptor) that bends downwards, giving the flower spike its wispy, bristly appearance.
The Banksia’s stamen (the pollen producing male reproductive organ) are tucked away in a small, spoon-like depression in the bud and as the flower opens and the style grows, it scrapes past the stamen. Collecting its own pollen onto a specialized tip on the style called a pollen presenter which it then “presents” to pollinators.
The Brown’s Banksia, like many Banksia species, produces a ton of nectar and its bright flower spikes are a rich food source for a diversity of animals. It flowers between March and August, peaking in June, and is pollinated by birds, like the New Holland Honeyeater, the Western Spinebill and the Red Wattlebird. By mammals like the Honey Possum and the Bush Rat. And by insects like the Western Honeybee and occasionally by flies and ants.
The Brown’s Banksia has a mixed-mating system, meaning it can both self-pollinate and cross-pollinate. An individual plant can pollinate itself and produce viable seeds, and/or it can be pollinated by other individuals of its species and produce viable seeds.
Once pollinated, the flower spike develops into a strong woody structure, looking a bit like a corncob embedded with dozens of follicles, these are tiny dry fruits, each holding a single seed.
These seeds are mainly dispersed by Serotiny. So, the small dry hard fruits remain on the plant, sealed, protecting the seed within, and do not open and release until they are exposed to fire. Generally the fire will kill the parent plant (it is not particularly fire-adapted) but in the process will release an accumulation of these stored seeds. The seeds have a tiny wing to aid in wind dispersal, drifting into ashen nutrient-enriched soils, well-cleared of competitors.
When the seeds germinate, they are slow growers, taking 5-8 years or more to reach reproductive maturity and needing roughly 15 years to build up an appreciable seed bank. In the absence of fire, individuals can live up to 50 years, though becoming less productive, more susceptible to disease and deterioration in old age.
So fire, and the frequency of fires, play a critical role in the Brown’s Banksia’s lifecycle. Too frequent fire kills individuals before they can reproduce, or build up a significant seed store. And with too infrequent fire, seeds are not released, populations simply do not reproduce, and decline into deteriorating old age.
In The Dream
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In the dream
The waiting, the season upon season, limbs aching, the promise of renewal heldfast though crumbling, a thousand tiny winged maybes, a thousand tiny futures deferred, a thousand questions without answer; begging for the fire-kiss, for sleep, for release.
In the dream.
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Habitat
The Brown’s Banksia is native to southwestern Australia, to a roughly 1000 square mile area in the state of Western Australia between the Stirling Range and the southern coast. Its population is split between two distinct clusters, a higher elevation population scattered in and near Stirling Range National Park, and a lower elevation population near the coast and the Australian city of Albany.
Its northern population grows on the upper slopes of steep quartzite and sandstone peaks in rocky low-nutrient soils. Its southern population is found in coastal heathlands, growing in sandy low-nutrient soils.
This region is striking and beautiful, low growing vegetation across plains which swiftly give rise to the Stirling Range, an isolated chain of mountains first formed over 1 billion years ago. And that ancient tectonic collision has been slowly eroding ever since. Wind, rain, ice and snow wear away at the land. Softer rocks of the surrounding plains erode more readily than the tough quartzite of the peaks. This process is called differential erosion: the hardened rock remains, now high, isolated mountains, while the surrounding land is lowered into the flat plains we see today.
This is a Mediterranean climate, with warm summers of highs in the mid 80s°F. And winter lows that dip into the low 40s°F with occasional freeze and frost. The region sees roughly 30 inches of rainfall per year.
The Brown’s Banksia shares its habitat with:
Western Bristlebird, Southern Sandplain Sun-lizard, Western Ground Parrot, Red Wattlebird, Western Rosella, Stirling Myrtle, South-western Cool Skink, Western Spinebill, Plant Louse, Western Brush Wallaby, Fairall’s Honeysuckle, Stirling Range Tapered Snail, New Holland Honeyeater, Heath Dragon, Noisy Scrub-bird, Bush Rat, Western Ringtail Possum, Rufous Treecreeper, Honey Possum, Short-winged Grasshoppers, Western Whipbird and many many more.
Threats
The primary current threat to the Brown’s Banksia is a human introduced soil-borne water mould, called Phytophthora cinnamomi that causes a fatal root-rot disease. This mould is affecting plant species across Australia. Our banksia is particularly susceptible to this pathogen, studies estimate that when Brown’s Banksia is inflected only 5% survive.
The mould spreads through the movement of water and contaminated soil. Human activities, development, shipping, vehicle-use, foot traffic, are believed to have introduced and spread the disease throughout the continent. Though the blight is concentrated in southwestern Australia.
Additionally, fire management and human induced climate change resulting in shifts in the frequency of wildfire is affecting the species. As noted, the Brown’s Banksia is deeply reliant on cycles of wildfire to ensure reproduction and generational regeneration.
Lastly, low genetic diversity resulting from low population and the species self-pollination reproductive strategy is a longterm threat.
Conservation
Fortunately most of the Brown’s Banksia population is found in the protected wilderness of the Stirling Range National Park and it is legally protected. Scientists are studying ways to combat the Phytophthora cinnamomi mold and the root-rot disease.
And a successful translocation program has established three new populations of the species. These are groups of individuals moved to a complimentary habitat away from blight infected soils.
The Millennium Seed Bank Partnership, has collected and stored seeds of the Brown’s Banksia in long-term deep-freeze.
There is an off-site cultivation program in place at Kings Park and Botanic Garden in Perth, with a living collection and a research program focused on the species’ genetics, disease resistance, and propagation.
Nevertheless the Brown’s Banksia has been considered critically endangered on the IUCN Red List since 2020 and their population is currently in decline.
Our most recent counts estimate that less than 1000 Brown’s Banksia remain in the wild.
Citations 24:04
Information for today’s show about the Brown’s Banksia was compiled from:
Australian Government’s Department of Climate Change, Energy, the Environment and Water – http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=8277
Barrett, S., Atkins, K., George, A. & Keith, D. 2020. Banksia brownii. The IUCN Red List of Threatened Species 2020: e.T112520669A113306481. – https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T112520669A113306481.en
Coates, D., Dillon, R., & Barrett, S. 2018. “Threatened Plant Translocation Case Study: ‘Banksia Brownii’ (Feather Leaved Banksia), Proteaceae.” Australasian Plant Conservation: Journal of the Australian Network for Plant Conservation 27 (1): 3-6. – https://doi.org/10.5962/p.373741
Coates, D.J., McArthur, S. L., Byrne, M. 2015. Significant genetic diversity loss following pathogen driven population extinction in the rare endemic Banksia brownii (Proteaceae), Biological Conservation, Volume 192, 2015, Pages 353-360. – https://doi.org/10.1016/j.biocon.2015.10.013
Day, D.A., Collins, B.G., Rees, R.G. (1997), Reproductive biology of the rare and endangered Banksia brownii Baxter ex R. Br. (Proteaceae). Australian Journal of Ecology, 22: 307-315. – https://doi.org/10.1111/j.1442-9993.1997.tb00676.x
Dillon, R., Coates D., Standish, R., Monks, L., Waycott, M. (2023) Assessing plant translocation success: common metrics mask high levels of inbreeding in a recently established Banksia brownii (Proteaceae) population. Australian Journal of Botany 71, 79-92. – https://doi.org/10.1071/BT22071
Gilfillan, Sandra & Barrett, S.R.. Feather-Leaved Banksia (Banksia Brownii) Interim Recovery Plan 2005-2010. – https://www.dcceew.gov.au/environment/biodiversity/threatened/recovery-plans/feather-leaved-banksia-banksia-brownii-2005-2010
Lamont Byron B., Enright Neal J., Witkowski E. T. F., Groeneveld J. (2007) Conservation biology of banksias: insights from natural history to simulation modelling. Australian Journal of Botany 55, 280-292. – https://doi.org/10.1071/BT06024
Renshaw, Adrian. The reproductive biology of four Banksia L.f. species with contrasting life histories. Doctor of Philosophy thesis. University of Western Sydney. 2005. – https://researchers-admin.westernsydney.edu.au/ws/portalfiles/portal/94886836/uws_3687.pdf
Sampson JF , Collins BG Coates DJ (1994) Mixed Mating in Banksia brownii Baxter ex R. Br. (Proteaceae). Australian Journal of Botany 42, 103-111. – https://doi.org/10.1071/BT9940103
Wikipedia – https://en.wikipedia.org/wiki/Banksia_brownii
For more information about Brown’s Banksia conservation please see the Australian government’s Department of Climate Change, Energy, the Environment and Water at https://www.dcceew.gov.au/.
Music 26:01
Pledge 31:33
I honor the lifeforce of the Brown’s Banksia. I will commit its name to my record. I am grateful to have shared time on our planet with this being. I lament the ways in which I and my species have harmed and diminished this species. I grieve.
And so, in the name of the Brown’s Banksia I pledge to reduce my consumption. And my carbon footprint. And curb my wastefulness. I pledge to acknowledge and attempt to address the costs of my actions and inactions. And I pledge to resist the harm of plant and animal kin and their habitat, by individuals, corporations, and governments.
I forever pledge my song to the witness and memory of all life, to a broad celebration of biodiversity, and to the total liberation of all beings.
