The golden age of species exploration could be now

ImageQuentin Wheeler writes a nice piece for National Geographic on why we should spend the money and effort to discover Earth’s species — before it’s too late.

If we play our cards right, the 21st century will be remembered as the golden age of species exploration.

No future generation will ever have the opportunities that we do to explore the results—all 12 million of them—of billions of years of evolution. Earlier generations of taxonomists lacked the travel, communication, and data management tools to complete an inventory of life on a planetary scale, and future generations will live in a world in which much of the living diversity is gone.

I think it’s this kind of big picture thinking that sometimes inspires my students to step up and get involved in this important time in our Earth’s history.

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Some positive trends in documenting life on Earth

Worlds Smallest VertebrateThe world’s smallest vertebrate (Paedophryne amanuensis) was one of the new species described last year — out of an estimated 18,000.

Recently, a student in my environmental legislation class approached me and asked a really good question: “Doesn’t teaching about environmental issues year after year all the time get you down?  There are so many depressing things happening in the world.” This caught me off guard.  My first response was: “Actually, yes. Sometimes it does get me down.  How could it not?” But then we started talking about some of the positive trends and successes over the past few decades. Our discussion moved toward the fact that scientists continue to make progress discovering new species and answering one of the biggest questions in biology: How many species are there on our Earth?  That seemed to turn the conversation around.

So, I thought I’d put together a few stories that have recently caught my attention.

In 2012, approximately 18,000 new species were cataloged by scientists around the world, according to the International Institute for Species Exploration (IISE) at Arizona State University. In 2009, nearly 20,000 were documented. Each year, the IISE puts together a top ten list of newly described species … their list from 2012 includes some pretty amazing creatures, including a primate, the Lesula Monkey (Cercopithecus lomamiensis).  A primate?  We haven’t even identified all the primates?

The Lesula Monkey (Cercopithecus lomamiensis) -- a newly described species in 2012.

Even in Europe, birthplace of modern taxonomy, one study estimates that more than 700 new species are cataloged each year. That’s more than two species each day! And a good chunk of them are described by amateur taxonomists.

And a recent study gives hope that extinct species may not actually be gone but lurking somewhere.  The Hula painted frog, previous thought to have been extinct, has been seen a handful of times recently in Israel, apparently still hanging in there. New research suggests that this frog is the only species in its taxonomic group.

Hula painted frog

The Hula painted frog, rediscovered in Isreal

And one of my favorites … fifteen new species of birds have been described in Amazonia. One of them is the muppet-Bowie bird:

Over the past decade, we also seem to be getting closer to a good estimate of how many species actually exist on the planet. You would think that we would have some scientific consensus on this number, but take a look at any biology or environmental science textbook and you’ll find the same broad range quotes … between 5 and 100 million species. There’s a huge difference between 5 and 100 million!  And since our current list of named species is just 1.5 million it has seemed that we have a long way to go.

However, recent scientific studies appear to be narrowing in on the lower end of that huge range … somewhere around 10 million, perhaps less (though there is still a considerable difference of opinion).

For example, Costello et al. (2013) write in a recent article in Science (Can we name Earth’s species before they go extinct) that the number of species on our planet is 5 million — plus or minus 3 million.  Still a wide range, but smaller.  They also argue that it is within our abilities – with increased funding and research efforts, of course — to describe most of them within the next 50 years.

Another example of a lower and narrower estimate comes from Mora et al. (2011), who make a good case that there are around 8.7 million species — plus or minus 1.3 million. Carl Zimmer’s summary of their work raises some of the scientific issues that make the whole enterprise of naming species as challenging as it is.  For example, there is much greater uncertainty around groups of species that have been traditionally understudied, like fungi, which many push the total estimate higher. Additionally, these estimates are for eukaryotic organisms (bacteria are not included).

I’ll admit, it is a little disappointing that there might not be 100 million species living somewhere on Earth.  But since this post was supposed to focus on positive trends, I’ll be happy with the idea that we might actually be able — in the not-so-distant future — to list the species that share the planet with us (before many of them go extinct, that is).


Citations for Peer-Reviewed Sources:

Costello MJ, May RM, and Stork NE. 2013. Can We Name Earth’s Species Before They Go Extinct? Science 25 January 2013: 339 (6118), 413-416. DOI:10.1126/science.1230318

Fontaine B, van Achterberg K, Alonso-Zarazaga MA, Araujo R, Asche M, et al. (2012) New Species in the Old World: Europe as a Frontier in Biodiversity Exploration, a Test Bed for 21st Century Taxonomy. PLoS ONE 7(5): e36881. doi:10.1371/journal.pone.0036881

Mora C, Tittensor DP, Adl S, Simpson AGB, Worm B. 2011. How Many Species Are There on Earth and in the Ocean? PLoS Biol 9(8): e1001127. doi:10.1371/journal.pbio.1001127


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Three questions about climate change addressed by President Obama

In this year’s State of the Union address, President Obama made some very clear statements about climate change.  Much clearer and more direct than any other U.S. President we’ve had so far.  He even addressed “three questions about climate change” that usually get smashed up, tied in knots, and lead to a breakdown in a reasonable conversation on the subject.

The worst disagreements that I’ve had with other people about climate change are because we start talking about different things.  In our minds, we are trying to answer different questions.  Three different questions, really.

Here they are … along with how President Obama addressed each one … mostly:

1) Is our Earth’s climate changing?

Yes it is.  Perhaps this was a question that we could have reasonably spent time discussing during the 1980s and 1990s, but with more data and observations we need to put it to rest.  Obama brushes it away this way:

Now, it’s true that no single event makes a trend. But the fact is, the 12 hottest years on record have all come in the last 15.

However you want to state the facts and observations that we have amassed at this point, getting bogged down in a discussion of whether the Earth’s climate is changing is just a distraction.

President Obama may have felt comfortable stating that climate change is a fact because public opinion is now more on his side than ever.  According to a recent poll by the Duke Nicholas Institute, 84% of US citizens believe that the Earth’s climate is changing (50% are convinced, 34% say it’s probable), and this continues an upward trend (see left panel below).

Duke climate change poll lg

2) Are humans the cause of climate change?

This particular question is at the heart of most climate change disagreements.

The Duke study found that 54% of US citizens believe that human activity is causing climate change (see right panel above).  That’s a slim majority, for sure, but the number has increased over the past several years.  We’re now in the territory of believing that we could actually have an impact on the climate system (and could actually do something to fix it).

In contrast, the scientific community agrees overwhelmingly that climate change cannot be explained without including greenhouse gases.  The Intergovernmental Panel on Climate Change address this in their 2007 report in the section “Can the Warming of the 20th Century be Explained by Natural Variability?”

President Obama didn’t address this question directly, but made statements that indicate that he believes humans are at least partly a cause.  For example:

And over the last four years, our emissions of the dangerous carbon pollution that threatens our planet have actually fallen. But for the sake of our children and our future, we must do more to combat climate change.

Stating that “carbon pollution” is linked with climate change acknowledges the consensus of scientists that greenhouse gases are the strongest forces that are heating up our Earth’s climate.  It also acknowledges the decision of the US Supreme Court in 2007 (Massachusetts v. EPA) that carbon dioxide should be considered a pollutant under the Clean Air Act by the EPA (or else they must make a clear statement of why it is not).

3) What should we do about climate change?

Finally, here’s the big question that we should be spending most of our time discussing.   What should we do?  Carbon taxes?  Cap and trade?  Geo-engineer? Ratify the Kyoto Protocol? Market-based legislation? Do nothing and figure out how our society should adapt to climate change?

Here is President Obama’s answer:

I urge this Congress to get together, pursue a bipartisan, market-based solution to climate change, like the one John McCain and Joe Lieberman worked on together a few years ago.

But if Congress won’t act soon to protect future generations, I will.

I will direct my cabinet to come up with executive actions we can take, now and in the future, to reduce pollution, prepare our communities for the consequences of climate change, and speed the transition to more sustainable sources of energy.

That’s about as clear as you can get.  Legislation that supports a market-based solution or else regulation (probably under the Clean Air Act).  Nothing about international cooperation, though.  That’s another can of worms.

And this seems to be in line with public opinion (again).  The Duke study found that a majority of US citizens would favor regulation of greenhouse gases directly.  There is very weak public support for a carbon tax or cap and trade, which would likely be a better approach if  you look at the track record of our environmental laws.

We’ll see if anything comes of it over the coming months, but at least there is something clearly on the table.

What a difference ten years makes.

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The New Year (and back to Costa Rica soon)

Graciedog pose

The New Year is approaching and I’m looking backward and forward at the same time.  It’s been an incredible year … probably one of the most life-changing that I’ve had.  The biggest event is that two amazing kids have joined our family and so my day-to-day life, attention, and motivations have shifted dramatically.  When I started this blog last January (almost one year ago) and gave it the title “This Changing Life” I couldn’t have predicted that it would turn out to mean as much about my life as the science that I wanted to write about.  On top of all this, the six weeks that I spent in Costa Rica last spring for my sabbatical seems like it happened a decade ago.  But I’m itching to get back …

Which bring me to the other thing that I’m preparing for … traveling again with a group of students from Westfield State University to Costa Rica for a two-week course.  We leave this Friday.  If you want to follow along, I started a Tumblr blog: WSU in Costa Rica where I’ll be posting photos and stories of our trip there.  I’ve already started posting photos from past trips.

What will the coming year bring?  No one ever knows until it happens.  We all have hunches.

I hope yours is amazing.

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Large pulses of greenhouse gases from mangroves not fully appreciated (or understood)

CR mangrove rootsOn climate change, a recent study warns that we are not accounting for the full cost of altering mangroves and other coastal ecosystems.

If you have ever visited a mangrove, you probably traveled by water.  Mangroves are a mixed-up tangle of roots and shallow, mucky organic sediments that are almost impossible to travel through by foot.  This tangle of roots, however, partly defines some of the unique ecosystem characteristics (and benefits) of mangroves.

Mangroves are found along the coastlines of tropical regions in waters that are shallow, salty, and oxygen poor.  The roots of mangrove trees have adaptations that allow them to survive in this harsh environment.  Pneumatophores, for example, are specialized roots that stick up out of the sediment and into the air, allowing gas exchange (especially oxygen) with the atmosphere.

Overall, one of the benefits of mangroves is that they protect shoreline from storms and ocean surges, while limiting the movement of pollutants from the surrounding landscape to the ocean.  Some estimate that 35% of worldwide mangroves have been removed for coastline development, shrimp farming, and other human activities.  The photo shows the edge of a mangrove (left) that has been altered to create salt ponds (right) in Costa Rica:

mangrove and salinas

Globally, the most important benefit of mangroves (and other vegetated coastal ecosystems) is probably their ability to remove carbon from the atmosphere and store it away.  In waterlogged ecosystems decomposition is limited by the lack of oxygen, which leads to a large accumulation of organic matter (also called a “pool” or “stock” of carbon).

A study published in PLoS by Pendleton and colleagues suggests that the total carbon content in these systems is huge and poorly understood.  Their study considered three types of vegetated coastal ecosystems — marshes, mangroves, and seagrasses – and found that mangroves contained the most carbon.

“Mangroves contain the largest per-hectare carbon stocks and contribute approximately half the estimated total blue carbon emissions.”

“Blue carbon” is a term that’s increasing being used to describe the carbon stored by coastal ecosystems, but we have yet to fully understand the dynamics of how this type of carbon is stored and lost.

When researchers estimate the impact of removing mangroves — or any ecosystem — on climate change, they usually just calculate what their loss means to carbon sequestration.  Carbon sequestration is the amount of carbon taken out of the atmosphere each year and “locked up” somewhere for a long time.  Most ecosystems accumulate carbon every year, because the amount of carbon that enters the system (through photosynthesis) is usually larger than the amount that leaves it (as organisms respire).

Ecosystems don’t accumulate carbon at the same rate, so we need to know how much carbon enters and exits each ecosystem separately.  In other words, you can’t study how this process works in tropical forests and apply it to mangroves.  Cut down tropical forests for pastures and we lose their ability to sequester carbon.  Clear away mangroves and replace them with buildings, fisheries, and salt ponds and they can no longer take carbon dioxide out the atmosphere and store it in their sediments.

The difference with mangroves is that they store a lot more carbon that tropical forests:

“Disturbance of the carbon stored in the biomass and top meter of sediment in a typical hectare of mangrove could contribute as much emissions as three to five hectares of tropical forest”

Their study demonstrates that we have been leaving out a large part of the carbon sequestration equation (literally)  — the large pulse of carbon that enters the atmosphere when a mangrove is removed.

“Indications are that such ‘pulse’ releases may have the largest and most immediate impact on greenhouse gas (GHG) emissions, possibly amounting to 50 times the annual net carbon sequestration rate.”

So, removing mangroves leads to a large pulse of carbon immediately into the atmosphere as well as the removal of an ecosystem that could take a lot of carbon from the atmosphere in the future.

Recently, the movement to quantify and document “blue carbon” has gained momentum in the conservation community.  Emerging global markets for carbon credits might offer a real economic incentive to protect mangroves … including the carbon that is already stored in the deep organic sediments, not just the potential for future storage, which makes mangrove carbon storage an economic alternative to ripping them out.  What we need is better information on the abundance of these types of coastal ecosystems on the planet and more detail on how much carbon is actually stored in them.

Pendleton L, Donato DC, Murray BC, Crooks S, Jenkins WA, et al. (2012)Estimating Global “Blue Carbon” Emissions from Conversion and Degradation of Vegetated Coastal Ecosystems.PLoS ONE 7(9):e43542.doi:10.1371/journal.pone.0043542

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Moth quietly meets demise by fungus

Creepy, fascinating, and just plain “wow-inspiring”, fungi that can control the behavior of insects are an incredible story from the files of evolution.  This moth likely met the end of its life at the hand (or mycelium?) of a Cordyceps fungusCordyceps is a genus of ascomycete fungi with at least 400 recognized species that are parasites of insects, arthropods, and other fungi.  A group of us came upon this unfortunate moth during a student course to Costa Rica that I led in January 2012.  We found it just days after one student had put finding one of the infamous fungi-infested insects at the top of her list.  (I wish she had given us her complete top ten list, we may have seen even more incredible things than we did.)

Although we couldn’t be completely certain that it was a Cordyceps infection, there were several tell-tail signs that it was.  First of all, the dead moth has a bunch of threadlike, fruiting bodies extending in all directions, which are responsible for dispersing spores.  Second, the moth died in an exposed location, which may have been orchestrated, zombie-like, by the fungus itself.  Cordyceps is known to have the ability to control an insect’s end-of-life wanderings, which it benefits from by increasing the likelihood that its spores are dispersed to new hosts.

Want to watch a Cordyceps infection in action?  Take a look at this incredible video clip:

So what’s an insect to do in the face of such a formidable parasite?  A recent study of ant colonies in Brazil found that there is a different parasite that uses Cordyceps as a host and essentially “castrates it” before the infection is complete.  This three-species interaction is another good example of the ecological complexity out there in the world that we are still, slowly getting a handle on.

If anyone has other ideas about what caused the demise of this moth, please let me know.

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Tiny insect continues to take down hemlock forests across eastern US

Severe damage to hemlock trees by the hemlock woolly adelgid

Alternate blog title: When is it time to give up on one of your favorite species?

Hemlock trees in eastern North America have been hit hard by a non-native insect, the hemlock woolly adegid. I’m fond of hemlock trees and would hate to see them go, but right now it seems inevitable that they are on their way out. This year has been a good one for the insect. Many new forests have been colonized by them, and trees that were already infested have seen a greater decline in health. Although it is too early to say with certainty, the warm winter and dry summer conditions seem to have been two direct punches in the gut at the same time.

Hemlock Woolly Adelgid Infestation

You can find a lot about the biology and spread of the hemlock woolly adelgid (often shortened to “HWA”) elsewhere, so I won’t go into detail here. Take a look at the links at the bottom of this page, especially the overview from the NY Invasive Species Clearinghouse. First identified in the 1950s in Virginia, the unintentional introduction of this Asian native has spread to its current distribution today, covering states from New England to Lake Erie and southward just about as far as hemlock trees live.

Older hemlock forests are spectacular places to spend time. The evergreen trees tower over the ground like giant architectural columns, creating a microclimate that is dark, moist, and cool. This microclimate is one reason why hemlock forests are so unique. Where hemlock trees exist along small streams, the temperature of the water is lower, which benefits fish and other aquatic organisms that thrive in colder temperatures. In addition to this, few plants can grow in the deep shade beneath these trees, so the understory is fairly open. The acidic soils and cooler microclimate tend to reduce the rate of decomposition, which leads to a thicker organic soil layer.

In addition to their ability to alter microclimatic conditions, hemlock trees can dominate large areas of a forested landscape, which is why some people call it a “foundation species”. Losing a foundation species from an entire landscape will certainly alter how these ecosystem function and change the habitats available to other organisms.

There are several reasons why we might have to let go of losing this species to a non-native insect. One is the unfortunate fact that hemlock trees don’t carry a clear economic value. Its wood is not as strong or sought after as oaks or even other conifers, and we don’t get syrup from it like sugar maples, the poster child for the campaign to stop the spread of the Asian longhorn beetle in eastern North America.

Another reason we might have to accept the decline of hemlock is that we don’t have a feasible way of stopping the spread of the adelgid insect. You can treat trees with fairly harmless horticultural oils each year or with pesticides every few years. However, it is much too expensive and tricky to treat an entire forest this way. Researchers are trying to identify a method of biological control. There are several organisms (especially beetles) from Asia that may be possible as well as a fungus, but no one has been able to demonstrate widespread success.

Hemlock forests have seen hard times in the distant past. Around 5500 years ago, they nearly vanished from the landscape during a period known as the mid-Holocene hemlock decline. The cause of this decline was likely a pathogen. Some researchers point to a fungus. Others have evidence that the hemlock looper (another insect) was to blame. There is also good reasoning (and some evidence) that climate changes at the time were involved, or at least there was an interaction between climate change and insect damage. Hemlocks eventually bounced back to become an important component of North American forests, but it took more than 1000 years to do so.

In graduate school, I spent several summers searching for old-growth stands of hemlock in northwestern Wisconsin, where hemlock trees reach their westernmost limit. If you travel farther westward, climate conditions are too dry for hemlock to get established and grow. It was a perfect situation for me to study how climate changes in recent ecological history (the past 2000 years) may have led to the expansion and contraction of hemlock’s distribution. Using pollen trapped in the mud of very small ponds (actually, tiny wet areas beneath the canopy of a forest) I helped develop a picture of the movement of the edge of a species range. In the case of hemlock it appears that small, outlying colonies developed first and then expanded rapidly hundreds of years later, perhaps during periods when climate conditions were conducive.

It’s funny that this appears to be how the adelgid spreads too. It is often found in forests beyond its range limit (probably traveling on the feet of birds), then spreads to fill in the space around it.

During my time stomping around in forests as a graduate student, I developed a deep fondness for hemlock trees. Today, when I pass one in a forest I take note of it. I look at where it’s growing, notice what other species are living nearby, and, of course, I turn over some of the branches to check for the adelgid. When I moved to Massachusetts in the late 1990s, the adelgid had just arrived in the state too. Now, 12 years later, the adelgid has been found in Vermont and northern New York.

Harvard Forest research scientist Dave Orwig has been studying the spread and impact of HWA in hemlock forests in New England since the mid-1990s. Along with others, he observed that the spread of the adelgids has been slower in Massachusetts. The trees have been hanging on longer when they do become infested compared to those just south in Connecticut. Many people say that the adelgid has reached its climatic limit and is showing signs of slowing down. However, the adelgid keeps popping up farther and farther north. Just a few years ago it would have been hard to find an adelgid in the Harvard Forest’s 3500 acres. This year, field crews are finding it in many of their research plots. This past winter’s warm temperatures may have had an impact, allowing more of the adelgids to survive and lay eggs well into the spring.

Cold temperatures may be the one thing that is going in our favor. Even though they are protected in winter by a woolly sac (its namesake), lab studies demonstrate that when temperatures dip below -30 degrees Celsius (-22 F) only 3% of the population survives. All of them die between -30 and -35 degrees C. But it’s tricky to put a number on it. A long cold snap of -20 degrees C may do the trick, at least to slow them down.

Even so, over time the adelgid populations may become better able to survive colder temperatures as the result of microevolution. Even if 95% of their population dies over the winter, there’s still 5% left that will produce offspring, which may be resistant to colder temperatures. In addition to this, a warmer future climate will allow them to continue their northward.

Elongate hemlock scale infestation

If this weren’t enough, another non-native insect(again from Asia) is also infesting hemlock trees – the elongate hemlock scale. It apparently interacts with HWA and competes for the trees resources, often doing better. The impact of the scale insect will likely still lead to tree death, but the process might take a little longer.

When I started teaching at Westfield State University, I started some small research projects with students to see what we were dealing with in western Massachusetts. Hemlock trees comprise a considerable fraction of the forest remnants around our campus and are a significant part of forests in the region. In one forest remnant we have been studying, HWA infestation was much higher in 2005-2008 than today. Since then, the elongate hemlock scale has become more common. The trees continue to die, but most of them are hanging on even after eight years of observations. Forests at higher elevations in our watershed are less likely to be infested, but over time we continue to find that adelgids are spreading. Some forests seem to be much more infested than others, even when they aren’t far from each other, which is a mystery. This year there seems to be a lot of personal observations of the adelgids showing up in places they hadn’t been seen before.

So, as a summary … here’s the status of hemlock and the adelgid in northeastern North America:

  1. The speed at which HWA has been spreading is slower than in mid-Atlantic and southern states, probably because of colder winter temperatures that kill some of the larvae.
  2. Although colder temperatures may be slowing its spread, the adegid continues to expand northward and may have done so very rapidly this year (2012) as a result of the warmer winter. In addition, over time the HWA populations may evolve to become more cold-hardy, and warmer temperature in the future may allow HWA to continue its spread.
  3. The elongate hemlock scale also infests hemlock trees. It tends to show up in forests following HWA infestation and may be less damaging than the adelgid (though it will still likely lead to tree death).
  4. Controlling HWA is possible with chemicals/soaps, but only cost-effective for a few trees (not entire forests). Biocontrol agents have had little success so far, but may be possible in the future.

All of this has led me to ask myself how much time we should spend working on an environmental problem that seems unsolvable. We have so few resources and time at our disposal and there are a lot of other environmental changes to work on. I don’t like being defeatist, but I do like to be realistic.

Still, I also like hemlock trees.


A few online resources …

US Forest Service Hemlock Woolly Adelgid website

Harvard Forest’s Hemlock Woolly Adelgid research page

NY Invasive Species Clearinghouse webpage on the Hemlock Woolly Adelgid

David A. Orwig, Jonathan R. Thompson, Nicholas A. Povak, Megan Manner, Donald Niebyl, David R. Foster. 2012. A foundation tree at the precipice: Tsuga canadensis health after the arrival of Adelges tsugae in central New England. Ecosphere 3(1): article 10. Published: January 26, 2012

Monique N. Lustenhouwer, Liza Nicoll, Aaron M. Ellison. 2012. Microclimatic effects of the loss of a foundation species from New England forests. Ecosphere 3(3): article 26. Published: March 26, 2012

As noted above, two photos originate from Nicholas_T at Flickr

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