Tag: climate change

A Plant Pathogen that Can’t Take the Heat

Plant pathogens have long been a thorn in the side of the agricultural industry, reducing crop production between 10-16 percent annually and costing an estimated $220 billion in economic losses (Chakraborty and Newton, 2011). What is more, there are concerns that such damages may increase in the future if temperatures rise as predicted by global climate models in response to CO2-induced global warming. Noting these concerns, Sabburg et al. (2015) write that “to assess potential disease risks and improve our knowledge of pathogen strengths, flexibility, weakness and vulnerability under climate change, a better understanding of how pathogen fitness will be influenced is paramount.”

In an attempt to obtain that knowledge, the team of four Australian researchers set out to investigate the impact of rising temperatures on Fusarium pseudograminearum, the “predominant pathogen causing crown rot of wheat in Australia” that is responsible for inducing an average of AU$79 million in crop losses each year. More specifically, they examined “whether the pathogenic fitness, defined as a measure of survival and reproductive success of F. pseudograminearum causing crown rot in wheat, is influenced by temperature under experimental conditions.”

The experiment was conducted in controlled-environment glasshouses at the Queensland Crop Development Facility in Queensland, Australia, where eleven lines of wheat were grown under four day/night temperature treatments (15/15°C, 20/15°, 25/15° and 28/15°C for 14-hour days and 10-hour nights). The first three treatments were representative of “the range of average maximum temperatures of the various wheat-growing regions across Australia,” whereas the fourth (28/15°C) treatment was intended to simulate a future warming scenario. The minimum temperatures of all treatments were kept at 15°C because “night-time temperatures over the last 50 years in the large majority of wheat-growing regions across Australia have not shown an increasing temperature trend in all seasons.” With respect to the eleven wheat lines, they were selected based on known susceptibilities and resistances to crown rot. Fourteen days after sowing a portion of each line was infected with F. pseudograminearum and then grown to maturity.

So what did the researchers find?

With respect to disease severity, Sabburg et al. report it was highest under the lowest temperature treatment and declined with increasing temperature (Figure 1a), and this general reduction was noted in all of the eleven wheat lines. Similarly, pathogen biomass was also reduced as treatment temperature increased (Figure 1b). According to the researchers, “on average, warming reduced pathogen biomass in stem base (PB-S) by 52% at either 25/15°C or 28/15°C compared with the biomass at 15/15°C.” And it also decreased the amount of relative pathogen biomass from the stem base to flag leaf node. (The flag leaf is to top leaf on the plant.)

A third fitness measure of F. pseudograminearum – deoxynivalenol (also known as “vomitoxin,” for an obvious reason) content (DON) – was also reduced in the stem base and flag leaf node tissue as temperature treatment increased. And the significance of this finding was noted by the authors as “an encouraging result if we consider temperature rises in the future,” because “DON can make food sources including wheat grains unsafe for human or animal consumption.” That’s putting it mildly!

Figure 1. Effect of temperature on (Panel A) disease severity as expressed by the length of stem base browning (cm) and (Panel B) relative pathogen biomass in stem base (PB-S) and flag leaf node tissue (PB-F) as measured by Fusarium DNA relative to wheat DNA. All measurements in wheat plants were made at maturity following stem base inoculation by Fusarium pseudograminearum. Adapted from Sabburg et al. (2015).

Figure 1. Effect of temperature on (Panel A) disease severity as expressed by the length of stem base browning (cm) and (Panel B) relative pathogen biomass in stem base (PB-S) and flag leaf node tissue (PB-F) as measured by Fusarium DNA relative to wheat DNA. All measurements in wheat plants were made at maturity following stem base inoculation by Fusarium pseudograminearum. Adapted from Sabburg et al. (2015).

In light of the above results, Sabburg et al. conclude that “this study has clearly established that temperature influences the overall fitness of F. pseudograminearum,” and that “based on our findings, warmer temperatures associated with climate change may reduce overall pathogenic fitness of F. pseudograminearum.” And given the annual production and monetary damages inflicted by this pathogen on wheat, this is news worth both reporting and celebrating!

 

References

Chakraborty, S. and Newton, A.C. 2011. Climate change, plant diseases and food security: an overview. Plant Pathology 60: 2-14.

Sabburg, R., Obanor, F., Aitken, E. and Chakraborty, S. 2015. Changing fitness of a necrotrophic plant pathogen under increasing temperature. Global Change Biology 21: 3126-3137.

 

You Say Meethane, I Say Meth-ane, Let’s Agree We Don’t Know Where It’s Coming From

Global Science Report is a weekly feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”

Atmospheric concentrations of methane (CH4)—a greenhouse gas many times more potent than carbon dioxide (at least over shorter time scales)—have begun rising after a hiatus from 1999-2006 that defied all expectations. No one knows for sure why—why they stood still, or why they started up again.

There is a lot of research underway looking into the causes of the observed methane behavior and at least three new studies have reported results in the scientific literature in the past couple of months.

The findings are somewhat at odds with each other.

In February, a study led by Alex Turner, from Harvard University’s School of Engineering and Applied Sciences, was published that examined methane emissions from the US over the past 10 years or so. The researchers compared observations taken from orbiting satellites to observations made from several sites on the earth’s surface. They reported over the past decade “an increase of more than 30% in US methane emissions.” And this increase was so large as to “suggest that increasing US anthropogenic methane emissions could account for up to 30-60% of [the] global increase.”

However, the methodologies employed by Turner et al. were insufficient for determining the source of the enhanced emissions. While the authors wrote that “[t]he US has seen a 20% increase in oil and gas production and a 9-fold increase in shale gas production from 2002 to 2014” they were quick to point out that “the spatial pattern of the methane increase seen by [satellite] does not clearly point to these sources” and added that “[m]ore work is needed to attribute the observed increase to specific sources.”

Perhaps most interestingly, Turner and colleagues note that “national inventory estimates from the US Environmental Protection Agency (EPA) indicate no significant trend in US anthropogenic methane emissions from 2002 to present”—a stark contrast to their findings, and a potential embarrassing problem for the EPA. But, never fear, the EPA is on it. The EPA is now actively re-examining its methane inventory and seems to be in the process of revising it upwards, perhaps even so much as to change its previous reported decline in methane emissions to an increase. Such a change would have large implications for the US’s ability to keep the pledge made at the U.S. 2015 Climate Conference in Paris.

However, the Turner et al. results have been called into question by a prominently-placed study in Science magazine just a couple of weeks later. The Science study was produced by a large team led by Hinrich Schaefer of New Zealand’s National Institute of Water and Atmospheric Research.

Schaefer and colleagues analyzed the changes in the isotopic ratios of carbon in the methane contained in samples of air within ice cores, archived air samples, and more recent measurement systems. Different sources of methane contain different mixtures of methane isotopes, related to how long ago the methane was formed. Using this information, the authors developed a model for trying to back out the methane sources from the well-mixed atmospheric samples. Although such a procedure is somewhat tunable (i.e., you can get pretty much any answer you want (kind of like climate models!)), the authors are pretty confident in their final results. 

No Temporal Decline in the Foxe Basin Polar Bear Population of Canada

Introducing their work, Stapleton et al. (2016) write that polar bears (Ursus maritimus) are “considered among the most highly sensitive marine mammals to the projected consequences of climate change,” citing Laidre et al. (2008). Indeed, increased sea ice losses projected for mid-century have led to concerns that “polar bears may be extirpated from or substantially reduced across most of the circumpolar Arctic.” As a result, the Arctic polar bear has become the proverbial canary in the coal mine for those seeking proof of climate change impacts in the far northern latitudes of our planet. Efforts have long been under way to study trends in these northern mammals and relate those trends to changes in climate.

The study of Stapleton et al. is no different in this regard. Their objective was to provide an updated analysis of the polar bear population within the Foxe Basin of Canada, a region that spans 1.1 million square kilometers across the Nunavut territory and northern Quebec. Last inventoried in the early 1990s, the Foxe Basin has been identified as a region of concern as climate conditions over the period 1979-2008 have led to a deterioration of the sea ice habitat (Sahanatien and Derocher, 2012) that has long been thought to engender a stable polar bear population. Against this backdrop of potential decline, Stapleton et al. set out to conduct an updated population survey of polar bears in this region to discern whether or not declining sea ice conditions had indeed affected their numbers as model-based projections claimed it would. And to this end, the three researchers conducted a series of aerial surveys in late summer of 2009 and 2010.

So what did their survey reveal?

NSF in Climate Denial?

Note:  David Wojick, who holds a doctorate in the history and philosophy of science, sent me this essay.  It is thought provoking and deserves a read.

The US National Science Foundation seems to think that natural decades-to-centuries climate change does not exist unless provoked by humans. This ignores a lot of established science.

One of the great issues in climate science today is the nature of long-term, natural climate change. Long-term here means multiple decades to centuries, often called “dec-cen” climate change. The scientific question is how much of observed climate change over the last century or so is natural and how much is due to human activities? This issue even has a well known name – The Attribution Problem.

 This problem has been known for a long time. See for example these National Research Council reports: “Natural Climate Variability on Decade-to-Century Timescales (NAP, 1995)” and “Decade-to-Century-Scale Climate Variability and Change (NAP, 1998). The Preface of the 1998 Report provides a clear statement of the attribution problem:

The climate change and variability that we experience will be a commingling of the ever changing natural climate state with any anthropogenic change. While we are ultimately interested in understanding and predicting how climate will change, regardless of the cause, an ability to differentiate anthropogenic change from natural variability is fundamental to help guide policy decisions, treaty negotiations, and adaptation versus mitigation strategies. Without a clear understanding of how climate has changed naturally in the past, and the mechanisms involved, our ability to interpret any future change will be significantly confounded and our ability to predict future change severely curtailed.

Thus we were shocked to learn that the US National Science Foundation denies that this great research question even exists. The agency has a series of Research Overviews for its various funded research areas, fifteen in all. Their climate change research area is funded to the tune of over $300 million a year, or $3 billion a decade.

The NSF Research Overview for climate change begins with this astounding claim:

Weather changes all the time. The average pattern of weather, called climate, usually stays the same for centuries if it is undisturbed.

This is simply not true. To begin with, there is the Little Ice Age to consider. This is a multi-century period of exceptional cold that is thought to have ended in the 19th century. Since then there have been two periods of warming, roughly from 1910 to 1940, and then from 1976 through 1998.  There’s real controversy about what happened since then.  Until our government joggled the measured ocean surface temperatures last summer, scientists could all see that warming had pretty much stopped—what happened has been attended to here, and to say the least, the new record is controversial. 

You Ought to Have a Look: Fighting DoE Efficiency Standards, Fracking to Go Global, and a ‘Hairy Panic’

You Ought to Have a Look is a feature from the Center for the Study of Science posted by Patrick J. Michaels and Paul C. (“Chip”) Knappenberger.  While this section will feature all of the areas of interest that we are emphasizing, the prominence of the climate issue is driving a tremendous amount of web traffic. Here we post a few of the best in recent days, along with our color commentary.

Let’s begin this installment of You Ought to Have a Look with a peek at the heroic attempt by Rep. Michael Burgess (R-TX) to try to reel in the fanatical actions by the Department of Energy (DoE) to regulate the energy usage (operation) of virtually all the appliances in your home. The DoE effort is being undertaken as part of President Obama’s broader actions to mitigate climate change as directed under his Climate Action Plan. It is an extremely intrusive action and one that interferes with the operation of the free market.

We have been pushing back (through the submission of critiques during the public comment period of each new proposed regulation), but the sheer number and repetition of newly proposed regulations spilling forth from the DoE overwhelms our determination and wherewithal.

Rep. Burgess’s newly introduced legislation seeks to help lighten our suffering.

Bill H.R. 4504, the “Energy Efficiency Free Market Act of 2016” would “strike all government-mandated energy efficiency standards currently required on a variety of consumer products found in millions of American homes.”

Burgess reasons:

“The federal government must trust the American people to make the right decisions when it comes to the products they buy. When the government sets the efficiency standard for a product, that often becomes the ceiling. I have long been a firm believer in energy efficiency; however, when the market drives the standard, there’s no limit to how fast and how aggressive manufacturers will be when consumers demand more efficient and better made products.”

“Government standards have proven to be unworkable. The Commerce Clause of the U.S. Constitution was meant as a limitation on federal power. It was never intended to allow the federal government to micromanage everyday consumer products that do not pose a risk to human health or safety.”

Current Wisdom: Swatting Away the Zika/Climate Change Connection

The Current Wisdom is a series of occasional articles in which Patrick J. Michaels and Paul C. “Chip” Knappenberger, from Cato’s Center for the Study of Science, review interesting items on global warming in the scientific literature or of a more technical nature. These items may not have received the media attention that they deserved or have been misinterpreted in the popular press.

We hardly need a high tech fly-swatter (although they are fun and effective) to kill this nuisance—it’s so languorous that one can just put their thumb over it and squish.

Jeb Bush’s candidacy? No, rather the purported connection between human-caused global warming and the highly-publicized spread of the Zika virus.

According to a recent headline in The Guardian (big surprise) “Climate change may have helped spread Zika virus, according to WHO scientists.”

Here are a few salient passages from The Guardian article:

“Zika is the kind of thing we’ve been ranting about for 20 years,” said Daniel Brooks, a biologist at University of Nebraska-Lincoln. “We should’ve anticipated it. Whenever the planet has faced a major climate change event, man-made or not, species have moved around and their pathogens have come into contact with species with no resistance.”

And,

“We know that warmer and wetter conditions facilitate the transmission of mosquito-borne diseases so it’s plausible that climate conditions have added the spread of Zika,” said Dr. Diarmid Campbell-Lendrum, a lead scientist on climate change at WHO.

Is it really “plausible?”

Hardly.

The Zika virus is transmitted by two species of mosquitoes, Aedes aegypti and Aedes albopictus, that are now widespread in tropical and sub-tropical regions of the globe (including the Southeastern U.S.), although they haven’t always been.

Spin Cycle: Green Tax Credits Supplant Clean Power Plan to Meet Our Paris Commitment

The Spin Cycle is a reoccurring feature based upon just how much the latest weather or climate story, policy pronouncement, or simply poo-bah blather spins the truth. Statements are given a rating between 1-5 spin cycles, with less cycles meaning less spin. For a more in-depth description, visit the inaugural edition.

The Obama Administration is involved in an all-out effort to soften the severity of blow that the U.S Supreme Court dealt the EPA’s Clean Power Plan (CPP) last week.*

In the day following the Court’s ruling, White House Deputy Press Secretary Eric Schultz referred to the Supreme Court’s stay as a “temporary procedural determination” and then added that “[i]t is our estimation that the inclusion of [the extensions of the renewable energy tax credits] is going to have more impact over the short term [on greenhouse gas emissions]than the Clean Power Plan.”

We covered Schultz’s first statement in our Spin Cycle from last week, giving it our top award of five Spinnies.

Here we examine the second part of his statement, that the extension of the investment tax credit (ITC) and the production tax credit (PTC) on solar and wind power, approved by Congress last December “is going to have more impact over the short term than the Clean Power Plan.”

On its face, we must admit this is true. Primarily because, under the CPP, the states aren’t required to begin cutting power plant emissions until 2022—far outside what we would consider “over the short term.” So, by the letter of the (now stayed) law, the CPP wouldn’t have to result in any greenhouse gas reductions prior to 2022. Schultz statement lacks the proper context. Walking (instead of driving) to lunch one time next week would also produce “more impact over the short term [on greenhouse gas emissions]than the Clean Power Plan” (stayed or not).