Climate change is happening in your garden: here’s how to spot it


Rebecca Darbyshire, University of Melbourne and Snow Barlow, University of Melbourne

As the weather warms and days lengthen, your attention may be turning to that forgotten patch of your backyard. This week we’ve asked our experts to share the science behind gardening. So grab a trowel and your green thumbs, and dig in.

Spring arrives and the warming weather encourages the plants in our gardens and parks to burst into life, commencing their annual reproductive cycle.

Plants use cues from the weather and climate to time their growth, flowering and fruiting. But as the world heats up due to climate change, these patterns are changing.

So how is climate change affecting our gardens, and what can we do about it?

In sync with climate

Many temperate plants have evolved to reproduce in spring to avoid damage from extreme cold or heat. Warmer conditions tend to speed up these processes, causing plants to grow faster.

Plants have evolved sophisticated mechanisms to synchronise with climate. This means they are excellent bio-indicators of climate change.

We know from global assessments that most plants studied so far are behaving as we’d expect them to in a warming world. Studies in the Southern Hemisphere have found the same.

In Australia, plants in southern Australia are maturing earlier – winegrapes, for instance, by 27 days on average between 1999 and 2007. We can see this in wine growers’ records. As you can see in the handwritten chart below, wine grapes are on average maturing (measured by their sugar content) earlier.

Grower-recorded winegrape maturity through time. Sugar content (oB) is the y-axis. Note the staple at the top of the page to accommodate early maturity in 2000 and 2007 .
Courtesy of Dr Leanne Webb

Other plants may behave differently. Fruit trees such as apples need cold weather to break buds from their dormant state, before commencing growth when warm temperatures arrive.

This means after warm winters, such as this one, flowering may actually be delayed. Data from a recent study show potentially delayed flowering for Pink Lady® apples, as you can see below.

Observed full-bloom timing for Pink Lady® in 2013.
Part of data set Darbyshire et al. (2016)

In the examples above, Applethorpe had the warmest spring and flowered first, as we’d expect for most plants. But Manjimup had the second-warmest spring and flowered last, even after Huon, the coldest spring site. This seems counter-intuitive but the delay is likely because Manjimup had the warmest winter.

Do these changes matter?

The earlier emergence of reproductive tissues may increase the risk of devastating frost damage. Contrary to what you might expect, evidence shows recent warming in southern Australia has not necessarily led to fewer frosts. On the other hand, plants that delay flowering because of warmer winters may reduce their frost risk.

Shifts in flowering timing, earlier or later, can be problematic for plants that rely on pollination between different varieties. Both varieties must shift flowering in the same way for flowering periods to overlap. If flowering times don’t overlap, pollination will be less successful, producing fewer fruit.

Bee and bird pollinators must also adjust their activity in sync with changes to flowering time to facilitate pollination.

Faster maturity may shift ripening into hotter times of year, as seen for wine grapes. This increases the risk of extreme heat damage.

Sun-damaged Pink Lady® apples in Western Australia
Rebecca Darbyshire

What about other changes?

Pests and diseases will also adjust their growth cycles in response to a changing climate. One pest well known to gardeners is the Queensland Fruit Fly (QFF). Their maggots are found in a wide range of fruits.

Climate change will likely favour fruit flies. Warmer temperatures for longer periods will encourage a higher number of generations each year. Meanwhile, reduced cold weather will mean fewer fruit flies will die, increasing the flies’ survival rates.

On the other hand, temperate pests and diseases may decrease if warming exceeds their temperature thresholds.

What can you do?

What have you observed? Citizen scientists who track the timing of biological events have provided valuable information, especially in Australia, for us to monitor and interpret plant responses to climate change. Keeping garden records will show if and how your plants or pests are changing their patterns.

If you observe your flowers emerging earlier, coverings can be used to protect against frost. Keep an eye on cross-pollinators – are they flowering together? If not, consider planting a different cross-pollinator.

Nets are an effective way to reduce heat damage and can also be used to protect against some pests. Setting pest traps according to weather rather than the calendar will help disrupt the first generation and reduce pest impact.

Climate change has already influenced biological responses, perhaps even in your own garden. Seeing these changes in our gardens gives us an insight into the significant challenges faced by our food production systems under a changing climate.

Adapting to current and future climate change is a reality, and is essential to preserve both the enjoyment we experience in our own gardens and the security of future food supply.

The Conversation

Rebecca Darbyshire, Research Officer, Climate Unit, NSW Department of Primary Industries and Lecturer, University of Melbourne and Snow Barlow, Foundation Professor of Horticulture and Viticulture, University of Melbourne

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

Record high to record low: what on earth is happening to Antarctica’s sea ice?


Nerilie Abram, Australian National University; Matthew England, UNSW Australia, and Tessa Vance, University of Tasmania

2016 continues to be a momentous year for Australia’s climate, on track to be the new hottest year on record.

To our south, Antarctica has also just broken a new climate record, with record low winter sea ice. After a peak of 18.5 million square kilometres in late August, sea ice began retreating about a month ahead of schedule and has been setting daily low records through most of September.

It may not seem unusual in a warming world to hear that Antarctica’s sea ice – the ice that forms each winter as the surface layer of the ocean freezes – is reducing. But this year’s record low comes hot on the heels of record high sea ice just two years ago. Overall, Antarctica’s sea ice has been growing, not shrinking.

So how should we interpret this apparent backflip? In our paper published today in Nature Climate Change we review the latest science on Antarctica’s climate, and why it seems so confusing.

Antarctica’s sea ice has reached a record low this year.
NASA, Author provided

Antarctic surprises

First up, Antarctic climate records are seriously short.

The International Geophysical Year in 1957/58 marked the start of many sustained scientific efforts in Antarctica, including regular weather readings at research bases. These bases are mostly found on the more accessible parts of Antarctica’s coast, and so the network – while incredibly valuable – leaves vast areas of the continent and surrounding oceans without any data.

In the end, it took the arrival of satellite monitoring in the 1979 to deliver surface climate information covering all of Antarctica and the Southern Ocean. What scientists have observed since has been surprising.

Overall, Antarctica’s sea ice zone has expanded. This is most notable in the Ross Sea, and has brought increasing challenges for ship-based access to Antarctica’s coastal research stations. Even with the record low in Antarctic sea ice this year, the overall trend since 1979 is still towards sea ice expansion.

The surface ocean around Antarctica has also mostly been cooling. This cooling masks a much more ominous change deeper down in the ocean, particularly near the West Antarctic Ice Sheet and the Totten glacier in East Antarctica. In these regions, worrying rates of subsurface ocean warming have been detected up against the base of ice sheets. There are real fears that subsurface melting could destabilise ice sheets, accelerating future global sea level rise.

In the atmosphere we see that some parts of the Antarctic Peninsula and West Antarctica are experiencing rapid warming, despite average Antarctic temperatures not changing that much yet.

In a rapidly warming world these Antarctic climate trends are – at face value – counterintuitive. They also go against many of our climate model simulations, which, for example, predict that Antarctica’s sea ice should be in decline.


Jan Lieser, Author provided

Winds of change

The problem we face in Antarctica is that the climate varies hugely from year to year, as typified by the enormous swing in Antarctica sea ice over the past two years.

This means 37 years of Antarctic surface measurements are simply not enough to detect the signal of human-caused climate change. Climate models tell us we may need to monitor Antarctica closely until 2100 before we can confidently identify the expected long-term decline of Antarctica’s sea ice.

In short, Antarctica’s climate remains a puzzle, and we are currently trying to see the picture with most of the pieces still missing.

But one piece of the puzzle is clear. Across all lines of evidence a picture of dramatically changing Southern Ocean westerly winds has emerged. Rising greenhouse gases and ozone depletion are forcing the westerlies closer to Antarctica, and robbing southern parts of Australia of vital winter rain.

The changing westerlies may also help explain the seemingly unusual changes happening elsewhere in Antarctica.

The expansion of sea ice, particularly in the Ross Sea, may be due to the strengthened westerlies pushing colder Antarctic surface water northwards. And stronger westerlies may isolate Antarctica from the warmer subtropics, inhibiting continent-scale warming. These plausible explanations remain difficult to prove with the records currently available to scientists.

Australia’s unique climate position

The combination of Antarctica’s dynamic climate system, its short observational records, and its potential to cause costly heatwaves, drought and sea-level rise in Australia, mean that we can’t afford to stifle fundamental research in our own backyard.

Our efforts to better understand, measure and predict Antarctic climate were threatened this year by funding cuts to Australia’s iconic climate research facilities at the CSIRO. CSIRO has provided the backbone of Australia’s Southern Ocean measurements. As our new paper shows, the job is far from done.

A recent move to close Macquarie Island research station to year-round personnel would also have seriously impacted the continuity of weather observations in a region where our records are still far too short. Thankfully, this decision has since been reversed.

But it isn’t all bad news. In 2016, the federal government announced new long-term funding in Antarctic logistics, arresting the persistent decline in funding of Antarctic and Southern Ocean research.

The nearly A$2 billion in new investment includes a new Australian icebreaking ship to replace the ageing Aurora Australis. This will bring a greater capacity for Southern Ocean research and the capability to push further into Antarctica’s sea ice zone.

Whatever the long-term trends in sea ice hold it is certain that the large year-to-year swings of Antarctica’s climate will continue to make this a challenging but critical environment for research.

The Conversation

Nerilie Abram, Senior Research Fellow, Research School of Earth Sciences; Associate Investigator for the ARC Centre of Excellence for Climate System Science, Australian National University; Matthew England, Australian Research Council Laureate Fellow; Deputy Director of the Climate Change Research Centre (CCRC); Chief Investigator in the ARC Centre of Excellence in Climate System Science, UNSW Australia, and Tessa Vance, Palaeoclimatologist, Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania

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

Putting carbon back in the land is just a smokescreen for real climate action: Climate Council report


Martin Rice and Will Steffen, Australian National University

Just as people pump greenhouse gases into the atmosphere by burning fossil fuels, the land also absorbs some of those emissions. Plants, as they grow, use carbon dioxide and store it within their bodies.

However, as the Climate Council’s latest report shows, Australia’s fossil fuels (including those burned overseas) are pumping 6.5 times as much carbon into the atmosphere as the land can absorb. This means that, while storing carbon on land is useful for combating climate change, it is no replacement for reducing fossil fuel emissions.

Land carbon is the biggest source of emission reductions in Australia’s climate policy centrepiece – the Emissions Reduction Fund. This is smoke and mirrors: a distraction from the real challenge of cutting fossil fuel emissions.

Land carbon

Land carbon is part of the active carbon cycle at the Earth’s surface. Carbon is continually exchanging between the land, ocean and atmosphere, primarily as carbon dioxide.

In contrast, carbon in fossil fuels has been locked away from the active carbon cycle for millions of years.

Carbon stored on land is vulnerable to being returned to the atmosphere. Natural disturbances such as bushfires, droughts, insect attacks and heatwaves, many of which are being made worse by climate change, can trigger the release of significant amounts of land carbon back to the atmosphere.

Changes in land management, as we’ve seen in Queensland, for example, with the relaxation of land-clearing laws by the previous state government, can also affect the capability of land systems to store carbon.

Burning fossil fuels and releasing CO₂ to the atmosphere thus introduces new and additional carbon into the land-atmosphere-ocean cycle. It does not simply redistribute existing carbon in the cycle.

The ocean and the land absorb some of this extra carbon. In fact, just over half of this additional carbon is removed from the atmosphere, and split roughly equally between the land and the ocean. However, this leaves almost half of the CO₂ emitted from fossil fuel combustion in the atmosphere. It’s this remaining CO₂ that is driving global warming.

Figure 2. Changes in the global carbon cycle from 1850 to 2014. Positive changes (above the horizontal zero line) show carbon added to the atmosphere and negative changes (below the line) show how this carbon is then distributed among the ocean, land and atmosphere.
Adapted from Le Quéré et al. 2015, data from CDIAC/NOAA-ESRL/GCP/Joos et al. 2013/Khatiwala et al. 2013.

Although Australia’s land sector has absorbed more carbon than it has emitted over the past decade or two, this has been overshadowed by our domestic fossil fuel emissions and those from our exported fossil fuels. These are roughly 6.5 times greater than the uptake of carbon by Australian landscapes.

Under international carbon accounting protocols, emissions are assigned to the country that burns the fossil fuels. However, many Australians are becoming increasing concerned about the ethics associated with exploiting our fossil fuels, no matter where they are burned.

In short, we’ve got a big problem that requires a global response, which includes a strong commitment from Australia.

Falling short of our commitment

Last December, Australia joined the rest of the world in pledging to do everything possible to limit global warming to no more than 2°C above pre-industrial levels, and furthermore to pursue efforts to limit the increase to 1.5°C. Yet Australia lacks a robust, credible long-term plan to cut Australia’s CO₂ emissions from fossil fuel combustion.

Current climate change policies and practices in Australia allow for the use of land carbon “offsets” – that is, carbon taken up by land systems can be used to offset or subtract from fossil fuel emissions. For example, the government’s Emissions Reduction Fund (ERF) provides financial incentives for organisations or individuals to adopt new practices or technologies that reduce or sequester greenhouse gas emissions.

Currently, vegetation (land system) projects represent the majority of ERF-accepted projects (185 out of 348). And yet, while storing carbon on land can be useful, it must be additional to, and not instead of, reducing fossil fuel emissions. Moreover, numerous critiques have questioned the effectiveness of the ERF.

Problems of scale

We also have a problem of scale. Reducing emissions through land carbon methods could save up to 38 billion tonnes of carbon globally by 2050 if combined with sustainable land management practices. By comparison, global carbon emissions from fossil fuel combustion are currently around 10 billion tonnes per year.

If this rate is continued, total fossil fuel emissions from 2015 to 2050 will be about 360 billion tonnes – nearly 10 times larger than the maximum estimated biological carbon sequestration of 38 billion tonnes over the same period.

It is now virtually certain that the carbon budget (the amount of carbon that can be produced while keeping warming below a certain level) will be exceeded. To meet the Paris 1.5°C aspirational target (and probably to meet the 2°C target) will require the use of negative emission technologies throughout the second half of the century.

However, no proposed negative emission technology has yet been proven to be feasible technologically at large scale and at reasonable cost, so this approach remains an in-principle option only. For effective climate action, the emphasis must remain on reducing emissions from fossil fuel combustion.

Using land carbon to “offset” our fossil fuel emissions is ultimately a smokescreen for real climate action.

Our thanks to Jacqui Fenwick for co-authoring this article and the report.

The Conversation

Martin Rice, Head of Research, The Climate Council of Australia and Honorary Associate, Department of Environmental Sciences and Will Steffen, Adjunct Professor, Fenner School of Environment and Society, Australian National University

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

Eastern quolls edge closer to extinction – but it’s not too late to save them


Bronwyn Fancourt, University of Tasmania

Eastern quolls – small, fleet-footed and ferocious – are one of Australia’s few surviving marsupial predators. They were once so common in southeast Australia that when Europeans arrived the quolls were reportedly hyperabundant.

But by the 1960s they were extinct on the mainland, driven down by a combination of disease, poisoning, persecution and predation.

Despite their mainland demise, eastern quolls continued to thrive in Tasmania – until recently. Across Tasmania, quoll numbers declined by more than 50% in the 10 years to 2009 and show no sign of recovery.

Recognising this worrying decline, the quolls have recently been listed as endangered internationally and in Australia. This is a stark reminder of how quickly a common species can plunge towards extinction.

But the quolls can still recover, as long as we act now while we still have an opportunity. In research published in Wildlife Research, I looked at what caused the decline, and how we can help.

Change in the weather

Several factors coincided with the decline, but after five years of investigation I found that a period of unfavourable weather was the most likely explanation.

Eastern quolls prefer areas with low rainfall and cold winters. But an 18-month period of warm winters and higher seasonal rainfall during 2002-03 resulted in most of Tasmania becoming unsuitable for eastern quolls. This rapidly drove their numbers down. In fact, the amount of environmentally suitable habitat in this period was lower than at any other time during the previous 60 years.

With the frequency of extreme weather events predicted to increase over coming decades, the future for eastern quolls looks uncertain.

Eastern quoll numbers declined as unfavourable weather conditions reduced the amount of environmentally suitable habitat across Tasmania (grey shading).
Fancourt et al (2015)

The predator pit

Interestingly, while weather conditions have since improved, eastern quolls have not recovered. With their numbers pushed so low, the remaining small populations can no longer breed faster than other threats kill them off. Historically, when quoll numbers were higher, they could cope with these threats.

Quolls are now trapped in what ecologists call a “predator pit”. Predators, cars, poison and a range of other threats are killing quolls as quickly as they can reproduce.

So population growth is in limbo – not because any threats have increased, but because small populations don’t have the capacity to outpace those same threats anymore.

Contrary to earlier predictions, feral cat numbers in Tasmania have not increased following declines in the Tasmanian devil population. Quoll populations could previously cope with the loss of a few quolls (mainly juveniles) to cats. However, that same number of quolls killed by cats is now potentially enough to wipe out any population growth, preventing the species’ recovery.

While feral cat numbers have not increased in Tasmania, cat predation of juvenile quolls could still be preventing their population from recovering.
Bronwyn Fancourt

Numbers game

The key factor preventing quoll recovery is their current small population. Quoll numbers need a boost, increasing reproductive capacity so that they can once again outpace the threats they are facing. This could be done by supplementing small, surviving populations in Tasmanian with quolls from captive-breeding colonies, insurance populations or the wild population on Bruny Island (which is doing better than mainland Tasmania).

Reducing feral cat numbers at key sites in early summer could also help reduce predation as juvenile quolls enter the population. That would potentially increase juvenile survival and allow quoll populations to grow and recover.

Increasing survival rates of juvenile quolls in the wild is key to helping the species recover.
Bronwyn Fancourt

Should quolls be reintroduced to the mainland?

Since word of the eastern quolls’ plight has spread, there has been increasing talk of reintroducing them to Australia’s mainland, where they disappeared more than 50 years ago. Such proposals are often well-intentioned and could potentially help restore some mainland ecosystems.

However, this could actually serve to drive wild populations in Tasmania closer to extinction, making the species’ recovery more difficult.

With only small populations persisting in the wild, removing only one or two individuals from a population could be enough to render that population functionally extinct – and once a population is functionally extinct it is on the path to total extinction.

Similarly, using quolls from captive colonies and insurance populations for mainland reintroductions further removes valuable quolls that could be used to repopulate and recover wild populations in Tasmania.

The eastern quoll’s persistence in Tasmania decades after it disappeared from the mainland suggests Tasmania is a far safer place for eastern quolls and offers them the best chance to recover. Removing them from a relatively safe place and reintroducing them to high-risk mainland sites filled with dingoes, foxes and toxic fox baits could actually hinder, not help, their recovery. For example, while baiting foxes may reduce the threat from foxes, it takes less than half of one fox bait to kill an adult female eastern quoll.

Mainland reintroductions should definitely be a goal in the longer term. But given the dangerously low numbers in Tasmania, we shouldn’t take Tasmanian quolls for high-risk mainland reintroductions until the Tasmanian population is safe. Once numbers in the wild have recovered, wild-sourced Tasmanian quolls could be reintroduced to mainland sites without putting wild populations at risk.

It’s time to act

Australia’s declining species face a slippery slope towards extinction. The key to recovery is understanding why the species declined, then acting while there is still time.

Australia’s history is littered with examples where delays and inaction prevented small populations from recovering, with some species now lost forever. The eastern quolls’ fate is not yet sealed. But we have to act now.

The Conversation

Bronwyn Fancourt, Honorary Research Associate, University of Tasmania

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

Current emissions could already warm world to dangerous levels: study


Andrew Glikson, Australian National University

Current greenhouse gas concentrations could warm the world 3-7℃ (and on average 5℃) over coming millennia. That’s the finding of a paper published in Nature today.

The research, by Carolyn Snyder, reconstructed temperatures over the past 2 million years. By investigating the link between carbon dioxide and temperature in the past, Snyder made new projections for the future.

The Paris climate agreement seeks to limit warming to a “safe” level of well below 2℃ and aim for 1.5℃ by 2100. The new research shows that even if we stop emissions now, we’ll likely surpass this threshold in the long term, with major consequences for the planet.

What is climate sensitivity?

How much the planet will warm depends on how temperature responds to greenhouse gas concentrations. This is known as “climate sensitivity”, which is defined as the warming that would eventually result (over centuries to thousands of years) from a doubling of CO₂ concentrations in the atmosphere.

The measure of climate sensitivity used by the Intergovernmental Panel on Climate Change (IPCC) estimates that a doubling of CO₂ will lead to 1.5-4.5℃ warming. A doubling of CO₂ levels from before the Industrial Revolution (280 parts per million) to 560ppm would likely surpass the stability threshold for the Antarctic ice sheet.

As the world warms, it triggers changes in other systems, which in turn cause the world to warm further. These are known as “amplifying feedbacks”. Some are fast, such as changes in water vapour, clouds, aerosols and sea ice.

Others are slower. Melting of the large ice sheets, changes in the distribution of forests, plants and ecosystems, and methane release from soils, tundra or ocean sediments may begin to come into play on time scales of centuries or less.

Other research has shown that during the mid-Pliocene epoch (about 4.5 million years ago) atmospheric CO₂ levels of about 365-415ppm were associated with temperatures about 3–4 °C warmer than before the Industrial Revolution. This suggests that the climate is more sensitive than we thought.

This is concerning because since the 18th century CO₂ levels have risen from around 280ppm to 402ppm in April this year. The levels are currently rising at around 3ppm each year, a rate unprecedented in 55 million years. This could lead to extreme warming over the coming millennia.

Temperature histories from paleoclimate data (green line) compared to the history based on modern instruments (blue line) suggest that global temperature is warmer now than it has been in the past 1,000 years, and possibly longer.
NASA, Author provided

More sensitive than we thought

The new paper recalculates this sensitivity again – and unfortunately the results aren’t in our favour. The study suggests that stabilisation of today’s CO₂ levels would still result in 3-7℃ warming, whereas doubling of CO₂ will lead to 7-13℃ warming over millennia.

The research uses proxy measurements for temperature (such as oxygen isotopes and magnesium-calcium ratios from plankton) and for CO₂ levels, calculated for every 1,000 years back to 2 million years ago.

Some other major findings include:

The Earth cooled gradually to about 1.2 million years ago, followed by an increase in the size of ice sheets around 0.9 million years ago, and then followed by around 100,000-year-long glacial cycles.

Over the last 800,000 years, and particularly during glacial cycles, atmospheric greenhouse gas concentrations and global temperature were closely linked.

The study shows that for every 1℃ of global average warming, Antarctica warms by 1.6℃.

So what does all this mean for the future?

Global warming past and future, triggered initially by either changes in solar radiation or by greenhouse gas emissions, is driven mainly by amplifying feedbacks such as warming oceans, melting ice, drying vegetation in parts of the continents, fires and methane release.

Current CO₂ levels of around 400ppm, combined with methane (rising toward 1,900 parts per billion) and nitric oxide (around 310ppb), are already driving such feedbacks.

According to the new paper, such greenhouse gas levels are committing the Earth to extreme rises of temperature over thousands of years, with consequences consistent with the large mass extinctions.

The IPCC suggests warming will increase steadily as greenhouse gases increase. But the past shows there will likely be abrupt shifts, local reversals and tipping points.

Abrupt freezing events, known as “stadials”, follow peak temperatures in the historical record. These are thought to be related to the Mid-Atlantic Ocean Current. We’re already seeing marked cooling of ocean regions south of Greenland, which may herald collapse of the North Atlantic Current.

A global temperature map for 2015 showing the cold water region in the North Atlantic Ocean.
NASA, Author provided

As yet we don’t know the details of how different parts of the Earth will respond to increasing greenhouse gases through both long-term warming and short-term regional or local reversals (stadials).

Unless humanity develops methods for drawing down atmospheric CO₂ on a scale required to cool the Earth to below 1.5°C above pre-industrial temperature, at the current rate of CO₂ increase of 3ppm per year we are entering dangerous uncharted climate territory.

The Conversation

Andrew Glikson, Earth and paleo-climate scientist, Australian National University

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