Acacia

Wiritjiribin is now drawing to a close. The season in the D’harawal calendar aligning with August, the last month of winter is behind us. Wiritjiribin is known to be cold and windy, and I remember it so for decades. My mother said August is a bad month. For someone of her vintage this was true, as not only is the weather cold and windy, but the number of deaths from influenza was higher in August than in the preceding two months, reflecting a pattern of sense-making in our temporal memories. In this case, anticipating news of loss.

At this time, the Earth is not tilting rapidly, although enough to notice. The Southern Hemisphere moving closer to the sun. The days lengthen. Ocean and air currents respond to temperature changes. Biota acclimates. Reproductive cycles turn. Seasonal biological patterns repeated every year, biodiversity intertwined with biogeography manifesting as temporally dynamic landscapes across the continent. A time for reflection.

For thousands of years human survival has been contingent on recognition of temporal and spatial patterns in the landscape, events that coincide with the flowering of a particular plant species, on attributing cause and effect, on anticipating what will happen next. Human survival is contingent on botanical literacy.

For Wiritjiribin, two Acacia species are offered as bookends. The flowering of Boo’kerrikin (Acacia decurrens) augurs the start of the season. This is when the fish start to run. The flowering of Marrai’uo (A. floribunda) augurs the end of Wiritjiribin and so the beginning of the next season, Ngoonungi (September – October). This is when the rains of spring usually begin. The D’harawal calendar features Acacia spp. for the seasons between the equinoxes, Kai’arrewan (A. binervia) the time of Parra’dowee (November – December), when it is warm and wet, and the eels migrate to the ocean. Weetjellan (A. implexa) flowering indicates Burran (January – March) when it is hot and dry. Meat is not eaten at this time as it spoils so readily in the heat.

Plants, specific plants, communicating key information with humans via their phenologies. Of course, there are more than these four Acacia species, in fact there are more than 1,000 different Acacia species endemic to Australia, many (most) with highly specific distributions. Subtleties in locations inviting speciation, leading to diversification and ecosystem complexity established over, in the case of Acacia, approximately 25 Mya.

Given our national flower is A. pycnantha – considered a symbol of unity – the significance of the Acacia genus extends across the continent by virtue of this fact alone. There is more to discover about Acacia species. I have recently read with great delight that “the power from the heavens” can manifest as gum “gum in the hearts of wattle trees”, this gum being “made by shooting stars lodging there and breaking into bits” (Clarke 2014). The inclusion of cultural knowledge of Aboriginal and Torres Strait Islander peoples affords deeper significance to these kinds of plant-human relationships. Further, based on the importance of Acacia to many Aboriginal people, Amnesty International proposed Australia Day be changed to 1 September, or Wattle Day, the first day of National Biodiversity Month.

Biodiversity is often explained in terms of a scientific measure to enable comparisons of species richness across time and place. By and large these measures monitor our own ecosystem vandalism. More recently, and reflecting our human-centredness, biodiversity is linked with human wellness (see UN Biodiversity and Health) to focus on the importance of ‘ecosystem services’.

Humans, as ever, sitting at the heart of the importance of this genus. With reference to Acacia spp., much of the readily available information about Acacia spp. lists the uses of various Acacia sp. as medicine, food, and wood for the making of artefacts.

Barely a nod is given to the flowering patterns of Acacia spp. being important to effective reading of the landscape and ensuring survival.

As I read the 2021 State of the Environment report’s Biodiversity section I wonder about how the glorious complexities of ecosystems are represented in reports; condensed, simple, readily digestible, largely offering depressingly downward trends. There is so much that we do not know; we are facing uncertainty and surround ourselves in an armour of metrics. Of course, our records are incomplete. Not all species have been documented, nor ever will be.

What we do know for sure is the number of extinctions events in Australia since colonisation is an under-representation (Woinarski et al. 2019). Action plans are crucial if we are to slow the frequency of extinctions. Silcock et al. 2021 have devised the National Action Plan for Imperiled Plants, where three of the 50 imperiled species listed are Acacia spp. This action plan makes it clear that there are ways to intervene to redress the injustice of extinction and conservation is key.

A locally important example is the Eastern Suburbs Banksia Scrub (ESBS). At the end of last year, this ecological community was reclassified by the Department of Climate Change, Energy, the Environment and Water as ‘critically endangered’ from ‘endangered’. Offering refugia for the plants that comprise the ESBS in urban gardens is crucial to maintain genetic diversity of these remnant populations.

In our own Curriculum Garden on the grounds of the University of Sydney we have focused on the Eastern Suburbs Banksia Scrub (ESBS). To date, three ESBS Acacia spp. have been planted (i.e., A. longifolia, A. suaveolens, A. ulicifolia). The garden was recently shortlisted for the Creating Impact (International) category in the Green Gown Awards.

Like my mother before me, and in light of the State of the Environment report, I have found August to be a time of grief. For as much as I am proud of the work we are doing in creating vegetation refugia, I grieve for the plants we have lost. These human-driven extinctions, these erosions of biodiversity, lost opportunities to learn about vegetation of this vast and wondrous continent.

Associate Professor Rosanne Quinnell is Deputy Director (Education) in SEI and a scientist and educator in the School of Life and Environmental Sciences, University of Sydney. She has taught botany for close to 25 years and is deeply committed to improving student engagement in science, particularly engagement with the botanical world by improving the botanical literacy within and outside of the classroom. Rosanne is redeveloping CampusFlora in collaborating with DVC ISS, ICT and NGNY with the re-release due before the end of 2022. Rosanne co-designed the Curriculum Garden in partnership the University Grounds staff and the Sustainability Strategy (planted 2021). Rosanne is leading the Living Laboratory in partnership with the University’s Sustainability Strategy, and she is an active member of the Sydney Indigenous Research Network.

Header image: Wattle by Anthony Rae via Unsplash.