Hi all. It has probably become obvious to anyone that may have been following this Blog for some time that posts have become few and far between of late. I think I have more-or-less struggled over the years with times of poor health, but no more so than the current time. It is a many faceted problem and I won’t go into all of the details. Essentially, something needs to change (or a number of things really). Being still at work and clearly needing to continue to work in order to feed myself, etc, sadly it has beome time to change the way I do things around my many Blogs, etc. I have always enjoyed being online and keeping blogs and websites ticking over, but it has now become an almost impossible chore.
What will change is that this Blog will remain up as an archive, while also providing a gateway (via a link) to my Facebook Page (Kevin’s Wilderness Journeys), where I hope to continue posting curated articles/links/reviews, etc. It is so much quicker and easier to do that there than having to write code, etc, here. Essentially, the only real change will be the location of the information. Of course, this will also affect the tumblr version of the Blog also. The page has been going for some time now, years in fact, and has long been a useful place for information concerning bushwalking and camping in Australia. Now it will the full range of environmental, wilderness, and all other manner of associated articles and news, as well as the bushwalking and camping emphasis.
If you would like to continue the journey with me, please visit the Facebook Page linked to below – and thank you for visiting me here over the years.
After three years of writing and two weeks of virtual negotiations to approve the final wording, the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC) confirms that changes are happening in Earth’s climate across every continent and every ocean.
My contribution was as one of 15 lead authors to a chapter about the oceans, the world’s icescapes and sea level change — and this is where we are now observing changes that have become irreversible over centuries, and even millennia.
Overall, the world is now 1.09℃ warmer than it was during the period between 1850 and 1900. The assessment shows the ocean surface has warmed slightly less, by about 0.9℃ as a global average, than the land surface since 1850, but about two-thirds of the ocean warming has taken place during the last 50 years.
The world’s oceans are warming and acidifying.Shutterstock/Damsea
We concluded that it is virtually certain the heat content of the ocean will continue to increase for the rest of the current century, and will likely continue until at least 2300, even under low-emissions scenarios.
We also concluded that carbon dioxide emissions are the main driver of acidification in the open ocean and that this has been increasing faster than any time in at least 26,000 years.
We can also say with high confidence that oxygen levels have dropped in many ocean regions since the mid-20th century and that marine heatwaves have doubled in frequency since 1980, also becoming longer and more intense.
Past greenhouse gas emissions, since 1750, mean we are now committed to future ocean warming throughout this century. The rate of change depends on our future emissions, but the process itself is now irreversible on centennial to millennial time scales.
A warming ocean is melting ice from below in West Antarctica.Shutterstock/Steve Allen
Ice loss in Antarctica
All this heat is bad news for the area I work in: Antarctica. With a warming ocean, the Antarctic ice sheet is left vulnerable to melting because so much of it rests on bedrock below sea level.
As the ocean warms and the ice sheet melts, sea level goes up around the world. We have very high confidence that the ice lost from West Antarctica in recent decades has exceeded any gain in mass from snowfall. We are also confident this loss has largely been due to increased melting of ice below sea level, driven by warming ocean water.
This melting has allowed the acceleration and thinning of grounded ice further inland — and this is what contributes to sea level rise. On the other side of the world, the Greenland ice sheet has also been losing mass over recent decades, but in Greenland this is principally due to warmer air, rather than warming ocean water.
It is virtually certain that the melting of the two great ice sheets, in Greenland and Antarctica, as well as the many thousands of glaciers around the world, will continue to raise sea levels globally for the rest of the current century.
By 2100, we project global mean sea level to be between 0.4m (for the lowest emission scenario, in which CO₂ emissions would have to drop to net zero by 2050) and 0.8m (for the highest emissions scenario) above the 1995–2014 average. How high the seas rise this century clearly depends on how much and how quickly we manage to cut greenhouse gas emissions.
The time to act is now
There are processes at play which we still cannot fully capture in computer models, mostly because they take place over periods of time longer than we have direct (satellite-based) observations for. In Antarctica, some of these uncertain processes could greatly accelerate the loss of ice, and potentially add one metre to the projected sea level by 2100.
Whether or not this worst-case scenario plays out or not remains uncertain, but what is increasingly beyond doubt is that global mean sea level will continue to rise for centuries to come. The magnitude of this depends very much on the extent to which we are able, collectively, to reduce greenhouse gas emissions right now.
Globally, the seas will continue to rise for centuries to come.Shutterstock/JivkoM
The scientific updates in our AR6 chapter are in line with those from previous assessments. That’s encouraging, because every assessment report brings in new authors with different expertise. The fact the scientific conclusions remain consistent reflects the overwhelming agreement within the global scientific community.
For our chapter, we have assessed 1500 research papers, but across the entire AR6, over 14,000 publications were considered, with an emphasis on recent research that hasn’t been assessed in previous IPCC reports.
The report has been scrutinised carefully at every stage of its evolution, attracting nearly 80,000 individual review comments from experts all over the world. Every single comment had to be addressed by the author team, with written responses provided and any changes to the text carefully noted and tracked.
What changes with each assessment is the clarity of the trends we are observing, and the increasing urgency with which we must act. While some aspects of AR6 are new, the underlying message remains the same. The longer we wait, the more devastating the consequences.
Click here to read more of The Conversation’s coverage of the IPCC report
Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.
I’ve heard the gravity changes when Antarctica melts will lower the seas around New Zealand. Will that save us from sea level rise?
The gravitational changes when Antarctica melts do indeed affect sea levels all over the world — but not enough to save New Zealand from rising seas.
The ice ages and their effects on sea level, geology, flora and fauna were topics of intense scientific and public interest all through the 19th century. Here’s how James Croll explained the “gravity effect” of melting ice in his 1875 book Climate and Time in their Geologic Relations:
Let us now consider the effect that this condition of things would have upon the level of the sea. It would evidently tend to produce an elevation of the sea-level on the northern hemisphere in two ways. First, the addition to the sea occasioned by the melting of the ice from off the Antarctic land would tend to raise the general level of the sea. Secondly, the removal of the ice would also tend to shift the earth’s centre of gravity to the north of its present position – and as the sea must shift along with the centre, a rise of the sea on the northern hemisphere would necessarily take place.
His back-of-the-envelope calculation suggested the effect on sea level from ice melting in Antarctica would be about a third bigger than average in the northern hemisphere and a third smaller in the south.
A more detailed mathematical study by Robert Woodward in 1888 has falling sea level as far as 2000km from Antarctica, but still rising by a third more than average in the north.
Woodward’s method is the basis of determining what is now called the “sea-level fingerprint” of melting ice. Two other factors also come into play.
The elasticity of the earth’s surface means the land will bounce up when it has less ice weighing it down. This pushes water away.
If the ice is not at the pole, its melting shifts the south pole (the axis of rotation), redistributing water.
Combining these effects gives the sea-level fingerprints of one metre of sea-level rise from either the West Antarctic Ice Sheet (WAIS) and Greenland (GIS), as shown here:
Fingerprints of sea-level change following melting of ice from West Antartica (WAIS) and Greenland (GIS) equivalent to one metre of sea-level rise on average. Red areas get up to 40% more than the average sea-level rise, blue areas get less. Author provided, CC BY-SA
Woodward’s method from 1888 holds up pretty well – some locations in the northern hemisphere can get a third more than the average sea level rise. New Zealand gets a little bit below the average effect from Antarctica, and a little more than average from Greenland. Overall, New Zealand can expect slightly higher than average sea level rise.
Combining the sea-level fingerprints of all known sources of melting ice, together with other known changes of local land level such as subsidence and uplift, gives a good fit to the observed pattern of sea level rise around the world. For example, sea level has been falling near West Antarctica, due to the gravity effect.
NOAA
Sea-level rise is accelerating, but the future rate is uncertain
The global average rise in sea level is 110mm for 1900-1993 and 100mm for 1993–2020. The recent acceleration is mostly due to increased thermal expansion of the top two kilometres of the oceans (warm water is less dense and expands) and increased melting of Greenland.
But the Gravity Recovery and Climate Experiment satellite has revealed the melting of Antarctica has accelerated by a factor of five in recent decades. Future changes in Antarctica represent a major source of uncertainty when trying to forecast sea levels.
Much of West Antarctica lies below sea level and is potentially subject to an instability in which warming ocean water melts the ice front from below. This would cause the ice sheet to peel off the ocean floor, accelerating the flow of the glacier towards the sea.
In fact, this has been directly observed, both in the location of glacial “grounding lines”, some of which have retreated by tens of kilometres in recent decades, and most recently by the Icefin submersible robot which visited the grounding line of the Thwaites Glacier, 2000km east of Scott Base, and found the water temperature to be 2℃ above the local freezing point.
The big question is whether this instability has been irreversibly set into motion. Some glaciologists say it has, but the balance of opinion, summarised by the IPCC’s report on the cryosphere, is that:
Observed grounding line retreat … is not definitive proof that Marine Ice Sheet Instability is underway. Whether unstable West Antarctic Ice Sheet retreat has begun or is imminent remains a critical uncertainty.
The IPCC special report on 1.5℃ concluded that “these instabilities could be triggered at around 1.5℃ to 2℃ of global warming”.
What’s in store for New Zealand
Predictions for New Zealand range from a further 0.46 metres of sea-level rise by 2100 (under a low-emission scenario, with warming kept under 2℃) to 1.05 metres (under a high-emission scenario).
A continued rise in sea levels over future centuries may be inevitable — there are 66m of sea level rise locked up in ice at present — but the rate will depend on how fast we can reduce emissions.
A five-year, NZ$7m research project, NZ SeaRise, is now underway, seeking to improve predictions of sea-level rise out to 2100 and beyond and their implications for local planning.
The independent review of Australia’s main environment law, released last week, provided a sobering but accurate appraisal of a dire situation.
The review was led by Professor Graeme Samuel and involved consultation with scientists, legal experts, industry and conservation organisations. Samuel’s report concluded Australia’s biodiversity is in decline and the law (the EPBC Act) “is not fit for current or future environmental challenges”.
The findings are no surprise to us. As ecologists, we’ve seen first hand how Australia’s nature laws and governance failure have permitted environmental degradation and destruction to the point that species face extinction. Even then, continued damage is routinely permitted.
And the findings aren’t news to many other Australians, who have watched wildlife and iconic places such as Kakadu and Kosciuszko national parks, and the Great Barrier Reef, decline at rates that have only accelerated since the act was introduced in 1999. Even globally recognisable wildlife, such as the platypus, now face a future that’s far from certain.
For example, the original distribution of the endangered southern black-throated finch of southern and central Queensland has shrunk to less than 10% due to land clearing and habitat degradation. Yet, further clearing was approved for coal mines, housing developments and sugar cane farms.
Biodiversity offsets, which aim to compensate for environmental damage by improving nature elsewhere, have for the most part been dreadfully ineffective. Instead they have been a tool to facilitate biodiversity loss.
Land clearing and cattle grazing are among the threats black-throated finches face. Stephanie Todd, Author provided
The centre piece of Samuel’s report are proposed new National Environmental Standards. These would provide clear grounds for drawing a line in the sand on environmental damage.
Legal, rigorous enforcement of these standards could turn around Australia’s centuries-long record of destroying its natural heritage, and curb Australia’s appalling extinction rate — while also providing clarity and certainty for business.
Vital features of the standards Samuel recommends include:
avoiding impacts on the critical habitat of threatened species
avoiding impacts that could reduce the abundance of threatened species with already small and declining populations
no net reduction in the population size of critically endangered and endangered species
cumulative impacts must be explicitly considered for threatened species and communities
offsets can only be used as a last resort, not as a routine part of business like they are at the moment.
Under the proposed National Environmental Standards, any new developments would need to be in places where environmental damage is avoided from the outset, with offsets only available if they’re ecologically feasible and effective.
2. Greater government accountability
The federal environment minister can make decisions with little requirement to publicly justify them.
In 2014, then environment minister Greg Hunt controversially approved an exemption to the EPBC Act for Western Australia’s shark cull. This was despite evidence the cull wouldn’t make people safer, would harm threatened species and would degrade marine ecosystems. Hunt could shirk the evidence, deny the impacts and make a politically expedient decision, with no mechanisms in place to call him to account.
Tiger sharks and white sharks were targeted in the WA cull. Shutterstock
Samuel’s report states the minister can make decisions that aren’t consistent with the National Environmental Standards — but only as a “rare exception”. He says these exceptions must be “demonstrably justified in the public interest”, and this justification must be published.
We think this epitomises democracy. Ministers can make decisions, but they must be open to public and robust scrutiny and explain how their decisions might affect environments and species.
Improved accountability will be one of the many benefits of Samuel’s proposed independent Environment Assurance Commissioner, which would be backed up by an Office of Compliance and Enforcement. Samuel says these must be free from political interference.
These are absolutely critical aspects of the reforms. Standards that aren’t audited or enforced are as worthless as an unfunded recovery plan.
3. Decent funding
Samuel urges improved resourcing because to date, funding to protect species and the environment has been grossly inadequate. For example, experts recently concluded up to 11 reptile species are at risk of extinction in the next 50 years in Australia, and limited funding is a key barrier to taking action.
Victoria’s grassland earless dragon (Tympanocryptis pinguicolla) is one of 11 reptile species identified as at risk of extinction. Michael Mulvaney/Wikimedia, CC BY-SA
And it has been proven time and again that lack of action due to under-resourcing leads to extinction. The recent extinction of the Christmas Island forest skink, the Christmas Island pipistrelle, and the Bramble Cay melomys were all attributable, in large part, to limited funding, both in the administration of the threatened species listing process, and in delivering urgent on-ground action.
Engaging experts is key to achieving Samuel’s long-overdue proposed reforms. He calls for the immediate creation of expert committees on sustainable development, Indigenous participation, conservation science, heritage, and water resources. This will help support the best available data collection to underpin important decisions.
Ultimately, though, much more investment in building ecological knowledge is required.
Australia has more than 1,900 listed threatened species and ecological communities, and most don’t even have active recovery plans. Ecologists will need to collect, analyse and interpret new, up-to-date data to make biodiversity conservation laws operational for most threatened species.
For example, while we know logging and fires threaten greater gliders, there’s still no recovery plan for this iconic forest possum. And recent research suggests there are actually three — not simply one — species of greater glider. Suspected interactions between climate change, fire and logging, and unexplained severe population declines, means significant new effort must be invested to set out a clear plan for their recovery.
Samuel recommends Regional Recovery Plans be adequately funded to help develop some knowledge. But we suggest substantial new environmental capacity is needed, including new ecological research positions, increased environmental monitoring infrastructure, and appropriate funding of recovery plans, to ensure enough knowledge supports decision making.
Cherry picking recommendations condemns our species
Samuel’s report has provided a path forward that could make a substantial difference to Australia’s shocking track record of biodiversity conservation and land stewardship.
But Environment Minister Sussan Ley’s response so far suggests the Morrison government plans to cherry pick from Samuel’s recommendations, and rush through changes without appropriate safeguards.
If the changes we outlined above aren’t implemented as a package, our precious natural heritage will continue to decline.
Federal and state governments on Friday resolved to streamline environment approvals and fast-track 15 major projects to help stimulate Australia’s pandemic-stricken economy.
The move follows the release this week of Professor Graeme Samuel’s preliminary review of the law, the 20-year-old Environment Protection and Biodiversity Conservation (EPBC) Act. Samuel described the law as “ineffective” and “inefficient” and called for wholesale reform.
At the centrepiece of Samuel’s recommendations are “national environmental standards” that are consistent and legally enforceable, and set clear rules for decision-making. Samuel provides a set of “prototype” standards as a starting point. He recommends replacing the prototypes with more refined standards over time.
By the end of August, the Morrison government wants Parliament to consider implementing the prototype standards.
But rushing in the new law is a huge concern, and further threatens the future of Australia’s irreplaceable natural and cultural heritage. Here, we explain why.
Rushing through changes to environment laws may damage nature in the long run. Rob Blakers/AAP
Semantics matter
Samuel’s review said legally enforceable national standards would help ensure development is sustainable over the long term, and reduce the time it takes to have development proposals assessed.
We’ve identified a number of problems with his prototype standards.
First, they introduce new terms that will require interpretation by decision-makers, which could lead the government into the courts. This occurred in Queensland’s Nathan dam case when conservation groups successfully argued the term environmental “impacts” should extend to “indirect effects” of development.
Second, there’s a difference in wording between the prototype standards and the EPBC Act itself, which might lead to uncertainty and delay. Samuel suggested a “no net loss” national standard for vulnerable and endangered species habitat, and “net gain” for critically endangered species habitat. But this departs from current federal policy, under which environmental offsets must “improve or maintain” the environmental outcome compared to “what is likely to have occurred under the status quo”.
Third, the outcomes proposed under the prototype standards might themselves cause confusion. The standards say, overall, the environment should be “protected”, but rare wetlands protected under the Ramsar Convention should be “maintained”. The status of threatened species should “improve over time” and Commonwealth marine waters should be “maintained or enhanced”, but the Great Barrier Reef Marine Park needs to be “sustained for current and future generations”.
And fourth, the standards don’t rule out development in habitat critical to threatened species, but require that “no detrimental change” occurs. But in reality, can there be development in critical habitat without detrimental change?
The Great Barrier Reef should be sustained for future generations. Jurgen Freund/AP
Mind the gap
The escape clause in the prototype standards presents another problem. A small, yet critical recommendation in the appendix of Samuel’s report says:
These amendments should include a requirement that the Standards be applied unless the decision-maker can demonstrate that the public interest and the national interest is best served otherwise.
Which decision maker is he referring to here – federal or state? If it’s the former, will there be a constant stream of requests to the federal environment minister for a “public interest” exemption on the basis of jobs and economic development? If the latter, can a state decision-maker judge the “national interest”, especially for species found in several states, such as the koala?
Samuel says the “legally enforceable” nature of national standards are the foundation of effective regulation. But both he and Auditor-General Grant Hehir in his recent report found existing enforcement provisions are rarely applied, and penalties are low.
Federal Environment Minister Sussan Ley has already ruled out Samuel’s recommendation that an independent regulator take responsibility for enforcement. But the record to date does not give confidence that government officials will enforce the standards.
Temporary forever?
Both Ley and Samuel suggested the interim standards would be temporary and updated later. But history shows “draft” and “interim” policies have a tendency to become long-term, or permanent.
For example, federal authorities often allow a proponent to cause environmental damage, and compensate by improving the environment elsewhere – a process known as “offsetting”. A so-called “draft” offset policy drawn up in 2007 actually remained in place for five years until 2012, when it was finally replaced. And the federal environment department recently accepted offsets based on the 2007 “draft” rather than the current policy.
The best antidote is to ensure the first tranche of national standards is comprehensive, precise and strong. This can only occur if genuine consultation occurs, legislation is not rushed, and the government commits to improving the “antiquated” data and information systems the standards rely on.
Environmental offsets allow a proponent to damage the environment in one location and improve it in another. WWF
Negotiation to the lowest bar
According to the Samuel report, the proposed standards “provide a clear pathway for greater devolution in decision-making” that will enable states and territories to conduct federal environmental assessments and approvals. This proposed change has been strongly and consistentlycriticised by scientists and environmental lawyers.
Ley also appears to be wildly underestimating the time and effort required to negotiate the standards with the states and territories.
Take the Gillard government’s attempts to overcome duplication between state and federal law by establishing a “one-stop-shop” approvals process. Prime Minister Julia Gillard pulled the plug on negotiations after a year, declaring the myriad agreements being sought by various states was the “regulatory equivalent of a Dalmatian dog”.
The Abbott government’s negotiations for a similar policy lasted twice as long but suffered a similar fate, lapsing with the dissolution of Parliament in 2016.
Samuel warned refining the standards should not involve “negotiated agreement with rules set at the lowest bar”. But vested interests will inevitably seek to influence the process.
Proceed with caution
We have identified significant problems with the prototype standards, and more may emerge.
Ley’s rush to amend the Act appears motivated more by wanting to cut so-called “green tape” than by evidence or environmental outcomes.
Prototypes are meant to be stress-tested. But if the defects are not corrected before hurrying into negotiations and legislative change, Australia might go another 20 years without effective environment laws.
Update: This article has been amended to reflect the national cabinet decision.
Stock markets around the world had some of their worst performance in decades this past week, well surpassing that of the global financial crisis in 2008. Restrictions in the free movement of people is disrupting economic activity across the world as measures to control the coronavirus roll out.
There is a strong link between economic activity and global carbon dioxide emissions, due to the dominance of fossil fuel sources of energy. This coupling suggests we might be in for an unexpected surprise due to the coronavirus pandemic: a slowdown of carbon dioxide emissions due to reduced energy consumption.
But prudent spending of economic stimulus measures, and a permanent adoption of new work behaviours, could influence how emissions evolve in future.
Global fossil CO2 emissions (vertical axis) have grown together with economic activity (horizontal axis) over extended periods of time. Glen Peters/CICERO
The world in crisis
In just a few short months, millions of people have been put into quarantine and regions locked down to reduce the spread of the coronavirus. Around the world events are being cancelled and travel plans dropped. A growing number of universities, schools and workplaces have closed and some workers are choosing to work from home if they can.
Even the Intergovernmental Panel on Climate Change has cancelled a critically important meeting and will instead hold it virtually.
The International Energy Agency had already predicted oil use would drop in 2020, and this was before an oil price war emerged between Saudi Arabia and Russia.
The unprecedented coronavirus lockdown in China led to an estimated 25% reduction in energy use and emissions over a two-week period compared to previous years (mostly due to a drop in electricity use, industrial production and transport). This is enough to shave one percentage point growth off China’s emissions in 2020. Reductions are also being observed in Italy, and are likely to spread across Europe as lockdowns become more widespread.
The emission-intensive airline industry, covering 2.6% of global carbon dioxide emissions (both national and international), is in freefall. It may take months, if not years, for people to return to air travel given that coronavirus may linger for several seasons.
Given these economic upheavals, it is becoming increasingly likely that global carbon dioxide emissions will drop in 2020.
Global air travel is down significantly as a result of the pandemic. Andy Rain/EPA
Coronavirus is not the GFC
Leading authorities have revised down economic forecasts as a result of the pandemic, but so far forecasts still indicate the global economy will grow in 2020. For example, the Organisation for Economic Cooperation and Development (OECD) downgraded estimates of global growth in 2020 from 3% (made in November 2019) to 2.4% (made in March 2020). The International Monetary Fund has indicated similar declines, with an update due next month.
Assuming the carbon efficiency of the global economy improves in line with the 10-year average of 2.5% per year, the OECD’s post-coronavirus growth projection implies carbon dioxide emissions may decline 0.3% in 2020 (including a leap year adjustment).
But the GFC experience indicates that the carbon efficiency of the global economy may improve much more slowly during a crisis. If this happens in 2020 because of the coronavirus, carbon dioxide emissions still could grow.
A decomposition of CO2 emissions growth into economic growth (orange) and carbon efficiency improvements (green) to estimate future emissions based on OECD economic growth projections. Glen Peters/CICERO
Under the worst-case OECD forecast the global economy in 2020 could grow as little as 1.5%. All else equal, we calculate this would lead to a 1.2% decline in carbon dioxide emissions in 2020.
This drop is comparable to the GFC, which in 2009 led to a 0.1% drop in global GDP and a 1.2% drop in emissions. So far, neither the OECD or International Monetary Fund have suggested coronavirus will take global GDP into the red.
The emissions rebound
The GFC prompted big, swift stimulus packages from governments around the world, leading to a 5.1% rebound in global emissions in 2010, well above the long-term average.
Previous financial shocks, such as the collapse of the former Soviet Union or the 1970s and 1980s oil crises, also had periods with lower or negative growth, but growth soon returned. At best, a financial crisis delays emissions growth a few years. Structural changes may happen, such as the shift to nuclear energy after the oil crises, but evidence suggests emissions continue to grow.
Global fossil CO2 emissions (in Gigatons or billions of tonnes of CO2) and carbon intensity of world Gross Domestic Product (grams of CO2 per $US, 2000), with the most important financial crises. Global Carbon Project
The economic legacy of the coronavirus might also be very different to the GFC. It looks more like a slow burner, with a drop in productivity over an extended period rather than widespread job losses in the short term.
Looking to the future
The coronavirus pandemic will not turn around the long-term upward trend in global emissions. But governments around the world are announcing economic stimulus measures, and they way they’re spent may affect how emissions evolve in future.
There is an opportunity to invest the stimulus money in structural changes leading to reduced emissions after economic growth returns, such as further development of clean technologies.
Also, the coronavirus has forced new working-from-home habits that limit commuting, and a broader adoption of online meetings to reduce the need for long-haul business flights. This raises the prospect of long-term emissions reductions should these new work behaviours persist beyond the current global emergency.
The coronavirus is, of course, an international crisis, and a personal tragedy for those who have lost, and will lose, loved ones. But with good planning, 2020 could be the year that global emissions peak (though the same was said after the GFC).
That said, past economic shocks might not be a great analogue for the coronavirus pandemic, which is unprecedented in modern human history and has a long way to go.
Coral habitats in the Great Barrier Reef (GBR) and in the Coral Sea support more than 1,000 fish species and a multitude of other animals. Our research, published in Nature today, documents the broader impact across the ecosystem of the widespread coral losses during the 2016 mass coral bleaching event.
While a number of fish species were clearly impacted by the loss of corals, we also found that many fish species responded to the increased temperatures, even on reefs where coral cover remained intact. The fish communities in the GBR’s southern regions became more like those in warmer waters to the north, while some species, including parrotfishes, were negatively affected by the extreme sea temperatures at the northern reefs.
One way to tease apart these various effects is to look at changes in neighbouring reefs, and across entire regions that have been affected by bleaching, including reefs that have largely escaped coral loss.
We were able to do just this, with the help of highly trained volunteer divers participating in the Reef Life Survey citizen science program. We systematically surveyed 186 reefs across the entire GBR and western Coral Sea, both before and after the 2016 bleaching event. We counted numbers of corals, fishes, and mobile invertebrates such as sea urchins, lobsters and giant clams.
Sea temperatures and coral losses varied greatly between sites, which allowed us to separate the effects of warming from coral loss. In general, coral losses were much more substantial in areas that were most affected by the prolonged warmer waters in the 2016 heatwave. But these effects were highly patchy, with the amount of live hard coral lost differing significantly from reef to reef.
For instance, occasional large losses occurred in the southern GBR, where the marine heatwave was less extreme than at northern reefs. Similarly, some reefs in the north apparently escaped unscathed, despite the fact that many reefs in this region lost most of their live corals.
Sea temperatures the culprit
Our survey results show that coral loss is just one way in which ocean warming can affect fishes and other animals that depend on coral reefs. Within the first year after the bleaching, the coral loss mostly affected fish species that feed directly on corals, such as the butterflyfishes. But we also documented many other changes that we could not clearly link to local coral loss.
Much more widespread than the impacts of the loss of hard corals was a generalised response by the fish to warm sea temperatures. The 2016 heatwave caused a mass reshuffling of fish communities across the GBR and Coral Sea, in ways that reflect the preferences of different species for particular temperatures.
In particular, most reef-dwelling animals on southern (cooler) reefs responded positively to the heatwave. The number of individuals and species on transect counts generally increased across this region.
By contrast, some reefs in the north exceeded 32℃ during the 2016 heatwave – the typical sea temperature on the Equator, the hottest region inhabited by any of the GBR or Coral Sea species.
Some species responded negatively to these excessive temperatures, and the number of observations across surveys in their northernmost populations declined as a consequence.
Parrotfishes were more affected than other groups on northern reefs, regardless of whether their local reefs suffered significant coral loss. This was presumably because the heatwave pushed sea temperatures beyond the level at which their populations perform best.
Nothing to smile about: some parrotfishes don’t do well in extreme heat. Rick Stuart-Smith/Reef Life Survey
Local populations of parrotfishes will probably bounce back after the return of cooler temperatures. But if similar heatwaves become more frequent in the future, they could cause substantial and lasting declines among members of this ecologically important group in the warmest seas.
Parrotfishes are particularly important to the health of coral reef ecosystems, because their grazing helps to control algae that compete with corals for habitat space.
A key message from our study is not to overlook the overarching influence of temperature on coral reef ecosystems – and not to focus solely on the corals themselves.
Even if we can save some corals from climate change, such as with more stress-tolerant breeds of coral, we may not be able to stop the impacts of warming seas on fish.
Future ecological outcomes will depend on a complex mix of factors, including fish species’ temperature preferences, their changing habitats, and their predators and competitors. These impacts will not always necessarily be negative for particular species and locations.
One reason for hope is that positive responses of many fish species in cooler tropical regions may continue to support healthy coral reef ecosystems, albeit in a different form to those we know today.
The link below is to an article that reports on the sea level changes that will occur around the equator due to rising sea levels caused by global warming and climate change.
One reason for hope is that positive responses of many fish species in cooler tropical regions may continue to support healthy coral reef ecosystems, albeit in a different form to those we know today.
Kevin's Walk on the Wild Side 
You must be logged in to post a comment.