An initiative of Earthwatch Institute

Scientist Q and A - Dr Tim Entwisle

Photo copyright Jaime Plaza
Photo by Jaime Plaza.

Dr Tim Entwisle is the Executive Director of the Botanic Gardens Trust, Sydney. He is a member of the ClimateWatch Community Engagement Panel and is a keen blogger (see Talking Plants). Here Tim talks to us about his interest in seasons and how ClimateWatch can help us become more ‘in tune’ with our seasons.

Why is the data collected through ClimateWatch of interest to you?
In Australia, we use seasons devised for the northern hemisphere. Why should they make any sense here? One view is that seasons are defined using day length and distance from the sun, and are the same everywhere around the world. But clearly we have a different climate and different seasonal changes when compared with London, or Singapore, or Reykjavik! More importantly, I think seasons should reflect what is happening in nature and when. As an example, come August or even late July, we notice a whole raft of plants starting to flower around Sydney and much of southern Australia. It is often commented that spring has come early, but this ‘early spring’ is one of our local seasons. That said, there is good evidence from around the world that certain plants are flowering earlier compared to say 30-40 years ago, however in Australia we don’t really have enough good data to say one way or another that our seasons are changing. This is where ClimateWatch is really valuable in that the general community can make observations on when things in nature are happening, helping our scientists to build up a long term dataset. Only then can we can start to track and understand our Australian seasons and the effects of climate change on our plants and animals.

You mentioned about seasons reflecting when things are happening in nature when, do you think our current seasons do this?
Good question! The climate varies around Australia, for instance winter in Hobart is markedly different from winter in Darwin, and I’m not even sure if Darwin knows what spring is! The Indigenous communities around Australia have tens of thousands of years experience and none of them use a four-season system. They base their calendars on local changes in climate, for instance when winds start, and also on when animals arrive and plants flower; hence Indigenous Australians have defined often between 6 and 8 seasons for any one place, with seasons varying from region to region. For the rest of Australia, a season starts when we flip a calendar! Spring is often described as the time when flowers start blooming and bees start buzzing. However in Sydney for instance, we see many plants start to bloom in August or even late July. This often sparks conversations that spring is starting early but I think we need to better understand our current seasons and seasonal changes before we can detect any changes that may be a result of a changing climate. This is where ClimateWatch can help build a better picture of when things in nature are happening and help inform what events are occurring in what season more accurately.

If you could redefine the seasons according to what is happening when, what would the seasons look like in your eye?
This topic is of particular interest to me but I’ll try and keep my answer short! There are six seasons recognised by the Dharawal people, south of Sydney, and I’m convinced there’s at least five. First of all, I like to celebrate our early spring, which I call ‘Sprinter’, when the bush bursts into flower. This is around August and September each year, even from late July in Sydney. After ‘Sprinter’ we would have what I call ‘Sprummer’, a changeable and often windy season from October to November. We then have a four-month summer through to March, followed by a two-month autumn (April – May) and two-month winter (June and July). There are lots of options but I do think the four-season system of Europe makes little sense in most parts of Australia. I’d be happy to have different seasons in different parts of the country. When you travel it would be part of the cultural experience. But if this seems all too hard, we could perhaps designate Floral Days – like Wattle Day – for each of these important seasonal shifts. First of all I’d like to move Wattle Day a month earlier to 1 August…!

How do you envisage the ClimateWatch data to be used?
As I’ve already touched on, the data could be used to help us get more ‘in tune’ with our seasons and establish what is really happening when. We can then start to understand if the changing climate is affecting the timing of these natural events, for instance flowering, which has been shown to be the case in the northern hemisphere. One of the great things about ClimateWatch too is that some international plant species are being monitored which will allow us to compare around the globe if there are similar trends in the timing – and any change in timing – of these events. Maybe our seasons, however they are defined, will have to evolve worldwide to keep pace with climate change…

What ClimateWatch species can people be looking out for now?
We are well and truly into spring (or sprinter!) so there are a whole range of species that can be monitored right now. Speaking from my area of interest, plants, there’s a good mix of natives and exotics. For instance the grevilleas and wax flower are blooming in the bushland environments, as well as the Silky Oak. A few other species include the Gymea Lily, Illawarra Flame Tree and English Oak. I know there are many more on the ClimateWatch website!

Silky Oak
A Silky Oak.

The ClimateWatch team would like to thank Dr Tim Entwisle for his time in this interview.