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How certain plants survive mass extinction events: study

How certain plants survive mass extinction events: study

We often read about Earth’s mass extinction events and how they wiped out vast numbers of animal species, leaving survivors to evolve and repopulate the planet. But it’s rarer to hear about how plants managed these catastrophes.

A new study published last month by a team at University College Dublin, Ireland, in the journal Nature Plants shows how plants with thicker, heavier leaves were more likely to survive the Triassic-Jurassic mass extinction caused by an episode of global warming 200 million years ago – around the time when dinosaurs came to dominate the planet. The extinction event is known to have had a massive impact on life, both on land and in the oceans, with an estimated half of species on Earth going extinct at the time.

“Previously we knew a bit about plant survival in terms of their abundance – whether they are present or absent in fossil record,” says the study’s lead author Wuu Kuang Soh, of University College Dublin, “but we didn’t know how they survived or the intrinsic factors of plants that contributed to their survival.”

By looking at fossilized leaves of two plant groups uncovered in Greenland, the authors suggest that the reason for some plants’ survival is that those with heavier leaves were more resilient to environmental stressors such as high air temperature and rising carbon dioxide.

According to Barry Lomax, a lecturer in Environmental Science at the University of Nottingham, UK, who was not involved in the research, “being able to establish that different plant groups respond differently to stress, and that their capacity to adapt to this stress is reflected in their propensity for survival, is a great piece of detective work.”

New proxy development

The work presented in this study – a joint research effort by University College Dublin and Macquarie University, Australia – relied heavily on the development of a new proxy i.e. a physical characteristic which is used to infer details about some related, but immeasurable, trait. By showing how the thickness of a plant’s leaf cuticle (the protective layer covering a leaf) is related to the leaf mass per unit area (LMA) in modern leaves, the team were able to use their fossils to identify how heavy the paleo leaves were for their size.

Macrofossil of 200 million years old Triassic ginkgo, Sphenobaiera spectabilis. Used with permission of the study authors (Credit: Mark Wildham).

For some scientists, this development itself is the study’s highlight. “I think the key finding of the work is that it gives us another set of tools to unpick how plants have responded to large scale perturbations in the carbon cycle which have influenced climate,” says Lomax.

By using the new proxy for LMA the authors were able to look at changes in two plant groups – Ginkoales (an gymnosperm order – see image) and Bennettitales (a now extinct order of seed plant)– across the Triassic-Jurassic mass extinction, and discover their opposing fates; the former flourishing and the latter experiencing sharp ecological decline.

“We found that plants with higher LMA had a higher chance of survival than plants with lower LMA during this global warming induced mass extinction event” says lead author Soh.

Commenting on the study, Charilaos Yiotis, a plant physiologist at University College Dublin who did not participate in the research, says that “under the greenhouse conditions of the Triassic-Jurassic Boundary – or, may I add, under near-future greenhouse conditions – plants with fast leaf turnover rates (low LMA) are outcompeted by those adopting more “conservative” strategies like robust, low turnover leaves (high LMA).” The turnover rate Yiotis refers to is the time taken for leaves to be produced and then fall.

“The spectrum describes how “fast” or “slow” the plant is turning over its nutrient resources,” adds Dana Royer, a paleobotanist at Weslayan University, Connecticut, who peer-reviewed the paper for Nature. “At the fast-return end (low LMA), plants have high photosynthetic rates, high nutrient contents, short-lived (deciduous, for example) and cheaply built leaves. This is the live-fast-die-young strategy. At the slow-return end (high LMA), plants show the reverse.”

The current mass extinction

The study’s findings are important in relation to the sixth mass extinction event which is currently underway. Scientists believe that a similar extinction process to those in the past is now taking place, as the variety of life on land gives way to the seemingly unstoppable human developments of agriculture, industry, and urbanisation. By looking at the paleo-evidence the authors tentatively suggest that today’s plant communities which host thicker, heavier leaves (high LMA) may be better adapted to deal with the current episode of anthropogenic warming, and therefore have a better chance of future ecological success than plants with lighter leaves (low LMA).

“More specifically, plants that can have leaves with both low and high LMA appear to do well after surviving a catastrophic mass extinction episode,” says Soh. “Our finding is important because it means that plants with flexibility in LMA will be the favourite to flourish during future global warming.”

“A shift to higher LMA is common for plants when they are exposed to high CO2” says Royer, “so the fact that the authors are finding the same response in a “natural” experiment – albeit 200 million years ago – lends support to the idea that we should expect a similar response in our own future.”

Further looking to the future, University College Dublin’s Charilaos Yiotis finds it alarming that most plants of economic importance today would probably never have made it through the Triassic-Jurassic Boundary.

“At a time where humanity’s biggest challenge is to feed an ever-growing human population,” he says, “this study should make us think again about how big a threat climate change is to future food security.”

By Conor Purcell, a Science & Nature Writer with a PhD in Earth Science.

Conor has previously worked with the authors of this paper, but not on the project itself. He can be found on twitter @ConorPPurcell and some of his other articles at cppurcell.tumblr.com.

References

Soh, W.K., Wright, K.L, Bacon, T.I., et al., Palaeo leaf economics reveal a shift in ecosystem function associated with the end-Triassic mass extinction event, Nature Plants, 3, doi:10.1038/nplants.2017.104, 2017.

Editor’s note: This blog post provides a summary to a research paper that is paywalled, unlike other scientific articles featured on GeoLog. The EGU supports and promotes open access, publishing 17 open access journals and having endorsed Open Access 2020, an initiative to promote the large-scale transition to open access publishing. Since research in the realm of palaeontology and evolutionary biology is rarely featured on GeoLog, an exception was made on this occasion to publish a story on a scientific paper not accessible to all. The lead author of the study is happy to be contacted with questions about the research; if you’d like to find out more please email Wuu Kuang Soh (wuukuang@gmail.com).

 

 

GeoPolicy: IPCC decides on fresh approach for next major report

GeoPolicy: IPCC decides on fresh approach for next major report

This month’s GeoPolicy post is a guest post from Sarah Connors, a Science Officer in the Intergovernmental Panel on Climate Change (IPCC) Working Group 1 Technical Support Unit (and former EGU Science Policy Officer). The IPCC is starting its sixth cycle, in which hundreds of scientists take stock of the world’s climate change knowledge by assessing the current scientific literature and then summarising this into three reports. These findings then play a vital role in supporting evidence-based climate policy around the world. The outlines, which focus on what each report will cover, were approved at a recent meeting in Montreal, Canada. This GeoPolicy post will summarise the new Working Group 1 outline and highlight how scientists can be authors in this IPCC cycle.

The process

Picture this, hundreds of delegates from countries all over the world descended on Montreal two weeks ago to discuss climate change. The gathering of all IPCC member states, known as the Plenary, occurs twice a year – this one was number 46. On the agenda was to discuss and approve the three Working Group (WG) outlines. These are lists of chapter titles and indicative bullets highlighting the topics that authors could focus on during their assessment. Almost 200 scientists drew up these proposed outlines in a meeting this summer in Addis Ababa, Ethiopia.

Each WG took it in turn to present their draft outlines to the Plenary. Country delegates then had the opportunity to ask for clarification and provide feedback, where needed. The WG Bureau (acclaimed scientists selected to steer this IPCC cycle) would then answer clarifying questions and note down all the suggestions from the floor. The Bureau then modified the outlines and presented them again to the Plenary, repeating the process as required until there was a consensus among all countries. With 195 countries being members of the IPCC, this made for long working sessions in Montreal, sometimes running late into the evening. But achieving consensus is a vital stage in the IPCC process. If all countries agree then it provides a strong platform for policy decisions to then be discussed.

The result was a huge success. All three WG outlines were accepted with minor changes (click to see the outlines for WG1, WG2, and WG3). We now have a new, easy-to-follow style for the next IPCC Working Group 1 report. In a nutshell, it will be more holistic and shorter, with increased focus on short-lived species, extremes, and regional information.

Working Group 1 (WG1) examines the physical science basis underpinning past, present and future climate change. The second working group (WG2) looks the vulnerability of socio-economic and natural systems to climate change, consequences and options for adaptation. The third working group (WG3) explores pathways for limiting greenhouse gas emissions, known as climate change mitigation.

What’s new in the WG1 report? A focus on the physical science basis…

As a Science Officer based in the WG1 Technical Support Unit (TSU), my role, along with my other TSU colleagues, was to keep track of the suggested outline changes and make sure the Bureau didn’t miss anything. The new outline has changed considerably compared to the last cycle (AR5), I think for the better.

Firstly, AR5 had more chapters (14 compared to 12), which were structured beginning with what we know about climate change from observations (inc. paleo data), followed by climate processes (i.e., biogeochemical cycles) and then finishing with climate modelling (i.e., model evaluation and projections). One reason being that the scientific community’s research is structured around these themes. The next assessment (AR6) outline however, is better suited to the report’s end-users, who usually prefer having everything about a given topic all in one place. Therefore, the AR6 report will be more holistic. For example, Chapter 3 (Human influence on the climate system) will assess observational, process, and modelling literature, whereas in AR5 this literature would have been spread across multiple chapters.

Comparing the AR5 and AR6 WG1 outlines

Secondly, the new report will be shorter. Since the first IPCC assessment, the WG1 report has dramatically increased in length. If this continues, projections show that the AR6 report would be almost 2000 pages long and would weigh just under 5kg! Rather than repeating the work of previous assessments, the new report will provide more of an update since the AR5, thus reducing its length.

Additionally, there will be greater focus on short-lived climate forcers (Chapter 6) and extreme events (Chapter 11) than in AR5. This may include assessing literature on how climate change and air quality are interconnected in Chapter 6 and the detection and attribution of single extreme events in Chapter 11.

Finally, there is a greater regional focus in the report’s final three chapters. Much of the information developed here will support further assessment in the WG2 report, which focuses on regional climate change impacts.

Happy members of the WG1 Bureau and Technical Support Unit after approval of the WG1 report outline. Photo credit: IISD/ENB | Mike Muzurakis

Getting involved in the next steps

With the outline agreed, the IPCC is now looking for authors to compile the report. Scientists are selected based on their expertise, publication record, and coordination skills. Regional diversity, gender and previous IPCC experience are all taken into account in the selection of authors to ensure broad representation. Roughly two-thirds of the authors are new to the IPCC each cycle. Once nominations close (27 October),  the authors will be selected and will get to work drafting the report. The whole process takes about four years, with the report planned for release in Spring 2021.

The IPCC actively encourages early career scientists (ECS) to participate in AR6, either as an author, an expert reviewer, or through publishing timely papers. Watch the video below for more information of ECS participation in AR6 or email the WG1 Technical Support Unit with any questions.

For more information please watch the YESS community youtube video on How can you get involved in the IPCC as an Early Career Scientist.

By Sarah Connors, Science Officer in the Intergovernmental Panel on Climate Change (IPCC)

Further reading:

The IPCC and the Sixth Assessment cycle

IPCC calls for nominations of authors for the Sixth Assessment Report

Guest post: What will be in the next IPCC climate change assessment

The Carbon Brief Interview: Valérie Masson-Delmotte

Imaggeo on Mondays: The shrinking of Earth’s saltiest lake

One of the consequences of the rapid fall of the water level (>1 m per year), is that vast areas of salt-rich ground of the shrunken Dead Sea are prone to strong dissolution and mechanical erosion of the subsurface processes.

The Dead Sea is one of the saltiest lakes on Earth, located at the lowest point of the globe.  For centuries it has been known for the restorative powers of its muds and waters. Their hypersalinity means it is possible to easily float on the lake’s surface.

Bordering Israel, the West Bank and Jordan, it is a unique environment in an otherwise arid region.  Changing climate, which is seeing temperatures rise in the Middle East, and the increased demand for water in the region (for irrigation) mean the areas on the banks of the lake are suffering a major water shortage. As a result, the lake is shrinking at an alarming rate.

The changing geomorphology of the Dead Sea region is now the focus of a large international project (DESERVE) to address the resulting geohazards at the Dead Sea.

One of the consequences of the rapid fall of the water level (>1 m per year), is that vast areas of salt-rich ground of the shrunken Dead Sea are prone to strong dissolution and mechanical erosion of the subsurface processes. This leads to the widespread land subsidence and the development of sinkholes, which pose a major geological hazard to infrastructure, local population, agriculture and industry in the Dead Sea area, writes Djamil Al-Halbouni in an abstract presented at the EGU 2016 General Assembly.

Today’s Imaggeo on Monday’s image was taken in the purpose of investigating the sinkhole phenomenon along the coastline.

“Near-surface aerial photography offer valuable hints on possible processes that lead to the formation of huge depression zones, e.g. the ground and surface water flow, the existence of vegetation and water sources or simply the morphology,” explains Djamil.

Sets of images are then combined into digital terrain models to quantitatively estimate hazard potentials and development of sinkholes via repeated measurements.

Specifically, this image was taken by a camera on a helikite balloon from 150m altitude. It shows a canyon penetrating the whitish pure salt shoreline at the Jordanian coast. It also reveals, in its’ magnitude surprising for the scientists involved, round structures under the shallow water, which are interpreted as submarine springs and possible submarine sinkholes close to the shore.

 By Laura Roberts and Djamil Al-Halbouni of the German Research Center for Geosciences, Physics of the Earth, Potsdam, German

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

GeoPolicy: What will a Trump presidency mean for climate change?

GeoPolicy: What will a Trump presidency mean for climate change?

The US Presidential election this month saw Republican Donald Trump, a fierce climate sceptic, be elected into office. In wake of the election results, this month’s GeoPolicy post will take a look at Trump’s proposed actions on climate change, how likely these are to happen, and what the climate and clean technology communities could do to limit the damage.

 

This tweet, written four years ago, has come to surmise Donald Trump’s views on climate change.

Beyond scepticism, reaching into the realms of conspiracy, it provides a dark outlook on what a Trump presidency might mean for global activities preventing climate change.

In his energy policy speech during his presidential campaign, Trump stated that he wants to re-ignite the US coal industry and expand oil and gas resources to strive for energy independence. Additionally, he has expressed a wish to “cancel” the Paris Agreement and retract Obama’s Clean Power Plan, which requires companies to lower their greenhouse gas (GHG) emissions1.

As President-elect, one of Trump’s first actions has been to appoint the renowned climate sceptic, Myron Ebell, to lead his US Environmental Protection Agency transitional team. Ebell has written much about climate change “alarmism” (as he describes it), has been quoted calling the Clean Power Plan “illegal” and the Paris Agreement “unconstitutional”2. Additionally, Trump favours Harold Hamm, Chief Executive of the oil company Continental Resources, to be his energy secretary3.

Perhaps in no surprise, the day after the election results, stock markets saw share prices rocket for coal companies and plummet for renewable energy firms4.

But will these plans be realised?

A recent news article from Science has tried to assess the possibility of Trump implementing his plans. Some are easier said than done5. The Paris Agreement was ratified by President Obama and entered into force on 04 November 2016. Legally, this means that Trump cannot immediately pull out of the Agreement, it would take several years. He could, however, remove the US from the U.N. Framework Convention on Climate Change (UNFCCC), which would take effect in one year. The article states that this is the most likely action Trump will choose to take. The US currently makes up 17.89 % of global GHG emissions6. It is the second largest contributing nation. Failing to reduce these emissions, or even increasing them, would be a substantial blow to the Paris Agreement.

 Entry Into Force of the Paris Agreement. Credit: Potsdam Institute for Climate Impact Research (https://www.pik-potsdam.de/)

Entry Into Force of the Paris Agreement. Credit: Potsdam Institute for Climate Impact Research (https://www.pik-potsdam.de/)

The Clean Power Plan, being domestic legislation rather than international, could be more difficult to revoke, as it has already undergone a lengthy review process. The article interviews Jody Freeman, director of the Environmental Law Program at Harvard Law School. Courts would have to approve the de-regulation of the Clean Power Plan and this would require ‘sound scientific or technical reasoning’, Freeman says5.

 

Beyond Paris

During the same week as the elections, COP22 was being held in Marrakesh. This meeting discussed the implementation of the Paris Agreement. The US Presidential announcement happened on the second day of the conference. Scientists’ responses were mixed. But a clear message resounded: with or without the US, the Paris Agreement will go ahead7.

Dr Philip B Duffy, former senior policy analyst in the White House Office of Science and Technology Policy, states in the video below, that there is an international momentum to tackling climate change that can’t be stopped. If the US government steps back then other countries must step up and do more.

One example of going above and beyond, is Germany, who has recently announced an agreement to cut carbon emissions by 95 % by 20508.

 

Another side to the argument?

It is clear that Trump does not care about climate change. What he has said, multiple times throughout his presidential campaign, is that he is a business man. Trump cares about making money.

Perhaps by putting the subject of climate change to the sidelines and focusing more on the economic arguments for transforming to a low-carbon technology it is possible to continue addressing this issue. Several economic arguments for tackling climate change exist9:

  • The cost of renewable energy sources have substantially decreased over recent years and the share of energy being produced by these methods is increasing10;
  • Natural disasters, like flooding and hurricanes, cost millions in damages and could become more frequent and severe due to climate change11. The rising damage and insurance costs are becoming more competitive with the investments needed to mitigate/adapt to climate change;
  • In the US, subsidies for traditional energy resources are four-times as large as they are for renewables12.

Several reasons now exist for switching to low-carbon energy supplies, which, in the process, reduce GHG emissions and mitigate against climate change. Additionally, a spokesperson from the Trump campaign did not disregard the possibility of developing renewable energy sources. They were quoted to say:

Energy independence means exploring and developing every possible energy source including wind, solar, nuclear and bio-fuels.  A thriving market system will allow consumers to determine the best sources of energy for future consumption.13

Many of Trump’s environmental policies focus on de-regulation: leaving it up to the individual States to choose whether they want to partake in mitigation policies. One small positive to this is that not all of the US shares Trump’s views, and although national policies may be changed, many States will continue to implement regional policies that promote clean technology and reduce GHG emissions5. But this will not be enough. If the US fails then the rest of the world must step up to limit rising global temperatures.

 

Further Reading:

The Trump Effect: Smaller than you think

Climate change a Chinese hoax? Beijing gives Donald Trump a lesson in history 

Sources:

[1] – How President Trump Will Affect Clean Energy and the Climate Change Fight

[2] – Trump Picks Top Climate Skeptic to Lead EPA Transition

[3] – Oil mogul Hamm tops Trump list for U.S. energy secretary: sources

[4] – 12 things that already happened within hours of Donald Trump being elected president

[5] – What Trump can—and can’t—do all by himself on climate

[6] – Paris Reality Check – pledged climate futures

[7] – Climate change: Nations will push ahead with plans despite Trump

[8] – German coalition agrees to cut carbon emissions up to 95% by 2050

[9] – Is there an economic case for tackling climate change?

[10] – Half of UK electricity comes from low-carbon sources for first time ever, claims new report

[11] – Tropical cyclones and climate change (Nature Geoscience)

[12] – Felipe Calderón: Economic Arguments Needed to Fight Climate Change

[13] – How President-Elect Trump Views Science