Mountain ash has a regal presence: the tallest flowering plant in the world

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CSIRO via Wikipedia, CC BY-SA

Gregory Moore, University of Melbourne

Welcome to Beating Around the Bush, a series that profiles native plants: part gardening column, part dispatches from country, entirely Australian. Read more about the series here or get in touch to pitch a plant at

The Indigenous people of Victoria and Tasmania have long known of the giant trees to be found in some of the wetter and cooler forests of these parts of Australia. The first Europeans were amazed to see trees of such stature growing in what they regarded as a dry and hostile environment.

The trees are straight and tall – almost incredibly tall – and many have massive girths. They are in every sense living giants.

Today we know the species by various common names, such as mountain ash, swamp gum, stringy gum or even giant gum, in different parts of Australia. Perhaps this is a situation where the proper botanical name, which many people find difficult and confusing, says it all. This monarch of eucalypts is officially called Eucalyptus regnans; regnans being Latin for ruling or reigning. Its massive stature gave rise to the name.

How does it grow?

Mountain ash lack many of the typical eucalypt adaptations to environmental stresses like fire, drought and poor soils. They compensate by growing very fast under the right conditions; eventually over-topping all the other species present.

They have huge and often deep root systems to supply adequate amounts of water. To grow successfully they need plenty of water and sunlight – so they are not really very hardy – but in the right environment they are unbeatable.

They always grow tall and so are not for your smaller suburban backyard, but there are many in backyards in the Dandenongs, in peri-urban sites to the east of Melbourne and in towns in Gippsland and the Otways.

Their mature leaves are about 3mm wide and can be as long as 150mm, while their flowers are white to cream in colour and 8mm across. The buds and flowers grow in clusters, but like the flowers of many eucalypts they often go unnoticed, especially on the taller trees. The fruits or gumnuts are again in clusters, about 10mm across and, somewhat surprisingly for such a large tree, contain hundreds of tiny seeds.

The bark is rough and fibrous at the base and for up to about 10m from the ground, but then is a beautiful smooth, mottled cream and grey with long ribbons of dead bark hanging from the canopy. These ribbons burn in bushfires and can carry fire for many kilometres ahead of a fire.

Read more:
Curious Kids: Where did trees come from?

A forest giant

We will never know if a Eucalyptus regnans was the tallest living thing on Earth; they are certainly the largest flowering plants in the world. Many of the biggest were felled in the mid to late 1800s before they could be properly measured.

There have been, and continue to be, a number of rivals for the tallest mountain ash; of course there have been the usual rivalries between states. Tasmania currently holds the record, but there are several tall specimens in Victoria that may take the crown in future.

Some of these trees were so large that the stumps could neither be transported from the forest, nor processed in the timber mills of the day. These huge logs can still be seen rotting on the forest floor more than a century later.

A stump of a Eucalyptus regnans in Tasmania’s Styx valley.
TTaylor/Wikipedia, CC BY-SA

These trees were so large, an old forester told me in the early 1970s, that when they felled them by hand with cross-cut saws, air could be heard being sucked into the cuts – the so-called sighing of the trees as they died.

We do know, however, that specimens of Eucalyptus regnans regularly exceed 85 metres in height and that one tree was measured at 132m tall. Often they were measured after they had been felled and the uppermost branches (and sometimes the stump) were not included in the measurement. Today the tallest specimens are just under 100m tall and the biggest tree is 10.74m in diameter and 33.75m in girth (measured at 1.4m above the ground).

They are second only to the coast redwood, Sequoia sempervirens, in height.

For such mighty trees, it often comes as a surprise that they are not as old as many people think. While the coast redwoods can exceed 2,000 years of age, mature Eucalyptus regnans tree are commonly about 300 years old, but may reach about twice that age if they are growing in the right place to miss bushfires.

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Sandpaper figs make food, fire, medicine and a cosy home for wasps

Vulnerable to fire

Mountain ash are easily killed by bushfires. Although they grow in the cooler and wetter parts of southeastern Australia where fires are not so frequent, as time passes, a fire becomes inevitable. The fire kills the individual specimens, but at the same time rejuvenates and renews the forest. The mighty Eucalyptus regnans regenerates from the tiniest of seeds that are shed from the woody fruits that were present in the canopy at the time of the fire; seedlings often emerge about six months after a fire.

When fires burn through Eucalyptus regnans-dominated wet forests most of the trees die, but those that don’t can be fire-scarred – often on one side. Over time these trees decay and then hollow out. Given their massive girths, they can develop huge cavities at the base and a hollow trunk leading upwards like chimney.

As with other similar large-girthed eucalypts, Indigenous people used these trees as shelters. They weren’t the only ones: there are records of early settlers and timber cutters using these trees as their homes for families of seven or more people.

Hollowed-out mountain ash were used as shelters by settler families.
State Library of Victoria

The timber from Eucalyptus regnans reminded some people of European ash timber and hence the name mountain ash, while others thought it had properties as good as oak and so the name Tasmanian or Tassie oak was used for the timber. The timber is still highly valued today and Eucalyptus regnans is a common plantation species in Australia and overseas.

The ConversationIn Victoria and Tasmania, Eucalyptus regnans forests are to be found within an hour’s drive of major cities, but in Melbourne, you can catch a glimpse of these magnificent trees and the forest over which they reign by visiting the atrium of the Melbourne Museum.

Gregory Moore, Doctor of Botany, University of Melbourne

This article was originally published on The Conversation. Read the original article.


New Zealand’s productivity commission charts course to low-emission future

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According to a recent report, New Zealand will need to increase renewable electricity generation, plant more trees and continue switching to electric transport more rapidly to achieve its zero carbon goal by 2050.
from, CC BY-SA

Robert McLachlan, Massey University

New Zealand has set itself a target of becoming carbon-neutral by 2050.

A recent report issued by the New Zealand Productivity Commission has found that this is an achievable goal, even under modest forecasts of technological progress and increases in carbon price.

Read more:
A fresh start for climate change mitigation in New Zealand

Rising emissions

New Zealand already had a goal of reducing greenhouse gas emissions to 50% below 1990 levels by 2050. That target had been in place since 2002, but emissions continued to rise through the 2000s.

An emissions trading scheme, which began operating in 2008, failed to stop the increase. A flood of imported cars increased New Zealand’s vehicle fleet and its emissions by 20% in just the past four years. A “wall of timber”, expected after 2020 as existing plantations are harvested, would further greatly increase net emissions under current carbon accounting rules.

Agriculture is responsible for an unusually large proportion — just under 50% — of New Zealand’s emissions. These emissions were rising too, especially long-lived nitrous oxides released by effluent and synthetic fertilisers.

A key part of New Zealand’s plan to meet global obligations had always been international carbon trading. However, in the Ukraine hot air scandal, low-integrity carbon credits were imported at rock-bottom prices. International trading was therefore suspended in 2015.

Aiming for zero

The Paris climate agreement made New Zealand’s “50 by 50” target — which the country wasn’t on track to meet — look distinctly weak. It has now become clear that only zero net emissions can stabilise temperatures, at any level, in the long run.

Read more:
A new approach to emissions trading in a post-Paris climate

It was in this context that New Zealand’s previous government asked the Productivity Commission to examine the “opportunities and challenges of a transition to a lower net emissions economy”. A few months into their work, the government changed and the new climate change minister, the Greens’ James Shaw, reinforced the urgency of the inquiry by asking the commission to consider the possibility of a net zero target for 2050.

The resulting 500-page report, now available in draft form, is a huge and comprehensive piece of work. From the very beginning, the commission knew what they were up against, writing that:

…the shift from the old economy to a new, low-emissions, economy will be profound and widespread, transforming land use, the energy system, production methods and technology, regulatory frameworks and institutions, and business and political culture.

The impact of widespread consultation, evidence and research is clear throughout. Although it is only advice, the report is a valuable resource for all future work on emissions reduction. It joins a chorus of similar (but much less detailed) studies issued recently.

Cost of carbon

The report finds that the carbon price required to get to zero net emissions in 2050 is fairly modest. In one model, it rises from its present price of NZ$21/tonne to NZ$55 in 2030 and NZ$157 in 2050 — within the NZ$100-250 range of global estimates consistent with the goal of keeping global temperature rise below 2℃. In other words, New Zealand does not have an unusually difficult decarbonisation challenge.

Although the report covers all main aspects of society and economy, there are three big changes that stand out:

  • Transport must be electrified rapidly (in some models, nearly all light vehicles entering the fleet must be zero-emission by the early 2030s)

  • Huge numbers of trees – up to an extra 2.8 million hectares, tripling the current plantation estate – must be planted to absorb carbon dioxide. These trees have to go somewhere, probably on sheep and beef farms

  • A lot of new renewable electricity generation will be needed, nearly doubling the present capacity, which is already 85% renewable.

Emissions trading can work

The meat of the report is the policies and institutions required to support and drive the transition. Key among them is a revised emissions trading scheme. So far the scheme has failed to reduce domestic emissions because the price of carbon was too low. This was driven mainly by low international prices, sector exemptions (including agriculture), and policy uncertainty which left businesses and investors unclear about future rules and prices.

The commission’s key recommended fixes include the adoption of a falling cap on emissions (to drive up prices and guarantee emissions reductions); a rising price cap (to prevent shocks to the economy and political resistance from emitters); and a rising price floor (to provide confidence to investors in low-emission technologies). Indeed, California’s system includes all of these elements and is currently on track to reduce emissions to 40% below 1990 levels by 2030.

Besides the emissions trading scheme, the report argues that every sector needs its own strategy. For example, on transport, it recommends an emissions standard – something most other developed countries except Australia currently have. Without this, New Zealand risks becoming a dumping ground for high-emission vehicles that manufacturers cannot sell elsewhere. They also recommend a “feebate” scheme, in which vehicles entering the fleet either incur a fee (if they have above-average emissions) or receive a rebate.

Risks and opportunities

I see a few key risks. First, trade-exposed industries, such as agriculture and food and metal processing, need to get discounts on carbon prices to remain competitive. A future in which each global industry decarbonises in a coordinated way does not seem likely, but each industry in each country still needs an incentive to clean up. This aspect remains difficult to deal with. For example, the recommendation that agriculture should be fully phased into the ETS is far outside the political mainstream in New Zealand at the moment.

The falling cap on emissions is an absolutely vital component, but it remains a decision that could be subject to lobbying in the aftermath of some domestic or international crisis.

In none of the report’s scenarios do gross emissions fall by more than 43% by 2050. This is certainly achievable, and it is in line with what some countries are doing right now, but it means New Zealand is relying heavily on tree planting to get to net zero. This is not a long-term solution – eventually you run out of space to plant more trees.

Although the commission has cast its net wide, it does not encompass all views. Political scientist Bronwyn Hayward, perhaps influenced by Trumpism, sees a climate commission as just another panel of experts telling us what to do. Without a fundamental renewal of democracy, this risks a backlash. Naomi Klein goes even further and views neoliberalism as being in kahoots with the fossil fuel industry as the enemy, with the only hope being youth activism.

The ConversationShe might not be wrong. In New Zealand, the idea for a Zero Carbon Act did originate with a youth group, Generation Zero. Their campaign has led fairly directly to this detailed road map for a zero carbon future. The next step, a public consultation about the Zero Carbon Act itself, kicks off this month.

Robert McLachlan, Professor in Applied Mathematics, Massey University

This article was originally published on The Conversation. Read the original article.

Australia’s Largest Wind Farm Approved in Queensland

The link below is to an article reporting on the approval of Australia’s largest wind farm in Queensland.

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