Constant as the Northern Star

Some species struggle to adapt to climate change

Change is afoot. Climate patterns across the globe are shifting as the planet steadily warms. That climate change is occurring is largely a settled issue in the scientific community. The debate has now shifted to questions of degree. How much will climates change? How will climate change impact living creatures?

Ecosystems are already feeling the strain. Summers are hotter, droughts are drier, and ocean acidification is well under way. But, preliminary studies suggest some species can adapt, changing food sources or migratory patterns to survive in altered environments.

Many plants, for example, are taking advantage of mild winters and early spring thaws by growing and flowering earlier than usual. This shift of springtime growth has real and dramatic consequences for the herbivores that feed on these plants. Will they change their behaviors to adapt to an earlier arrival of their smörgåsbord?

A long-term study published recently in PLoS Biology sheds light on this question. French and British scientists collected nearly three decades of reproductive data on roe deer, an important European herbivore. Roe deer mothers give birth to their young in spring for one very important reason: mothers rely on the rich, nutritious, and easily digestible springtime diet of young plant shoots to help them produce enough milk for their hungry offspring. But, the window for this vernal bounty is narrow; mothers who give birth too soon or too late miss the fresh vegetation and have less milk for their fawns. Critically, these deprived offspring are less likely to survive beyond their first year.

The French and British team analyzed a well-studied population of roe deer from the Trois Fontaines, a forest preserve of over 1,300 hectares in France’s historic Champagne province. They had access to 27 years of demographic data for local roe deer, including the number of offspring born to each mother and fawn survival rates. Over that same time period, they also knew the timing of springtime forest growth (based on meticulous records of flowering dates for nearby vineyards).

Timing is everything. Image credit: Jan Bo Kristensen.

Timing is everything.
Image credit: Jan Bo Kristensen.

Over the 27 year period (from 1985 to 2011), average springtime temperatures in the Trois Fontaines increased by more than 2.5°F. As a direct consequence, the fresh shoots of the season arrived two weeks earlier in 2011 than they did in 1985. But, amazingly, the roe deer in the preserve did not shift the timing of reproduction over the same period. As a result, mothers missed out on the rich diet of young forest shoots, and produced less milk for their offspring; fewer roe deer fawns survived their first year.

This worrisome trend dented roe deer population growth in the Trois Fontaines. In the long term, as temperatures continue to rise, the gap between springtime growth and roe deer births should widen further. This may dampen the roe deer population, depriving a complex forest ecosystem of a critical herbivore.

The findings of this study stand in stark contrast to observations from other animal species. For example, many birds have adjusted breeding times and locations to cope with changing climate. But, the roe deer of the Trois Fontaines are a reminder that not all species are currently capable of recognizing and adjusting to the impacts of humankind on global ecosystems. That may change; roe deer, for example, could migrate to areas where springtime growth dates are more synchronized with their reproductive cycles. But, for enclosed preserves like Trois Fontaines, this is not a viable option.

Why were roe deer unable or unwilling to adjust their reproductive cycles? One possible explanation might involve the cues they use to time reproductive activities. Some species use temperature as a sign that spring has arrived and it is time to breed; this strategy has built-in flexibility for adapting to climate change, since warmer weather and an early spring go hand-in-hand. But, roe deer appear to use photoperiod (day length) as a trigger for their reproductive behaviors. This may explain why roe deer mothers continued to give birth at the same time over three decades, even as their bountiful feast emerged earlier and earlier each year. After all, day length depends on Earth’s axial tilt and rotation, something humans have not yet learned to alter.

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Birds of a Feather

As we learn in our earliest playground adventures, cheaters are out there trying to exploit the labor of others.  Cheaters want to prosper, and sometimes they do.  For every Bernard Madoff languishing in prison, there could be another languishing in a Caribbean bungalow.  Societies are best served by mechanisms that dissuade cheaters, as the cheater’s gain is the honest man’s loss.  That is often easier said than done.

Humans are not the only creatures to face the scourge of cheating.  From microbes to animals, cheaters emerge in the simplest social interactions.  Successful tricksters pass along any genes that helped them cheat to the next generation, further upending social dynamics and forever altering a population’s genetic makeup.  Thus, the exploited are rightly pressured to discourage cheating.  But, what strategies are best to thwart cheaters on a long-term basis?  New observations in birds suggest cooperation is key.

Brood parasites are the ultimate cheaters of the avian playground.  These birds do not build nests to rear their chicks.  Instead, females lay their eggs in the nests of other species, tricking unwitting “adoptive” parents into caring for parasitic young.  Fooled host parents pay a high price in resources shunted away from their own biological offspring and toward their parasitic wards.  But, as a recent dispatch in Science magazine reports, some birds may have an effective strategy to keep the cheaters at bay.

Cooperation is the basis of this anti-cheater scheme.  Dr. Naomi Langmore and her team at Australian National University noticed an intriguing pattern in the global distribution of brood parasite species.  They almost exclusively overlap with birds known as cooperative breeders.  Cooperative breeders form complex social groups that defend nests, rear chicks, and even adopt orphans.  Dr. Langmore’s group was struck by the strong geographic overlap of brood parasites and cooperative breeders.  Within these ranges, brood parasites targeted cooperative breeders to rear their young.  Were the effective group parenting skills of cooperative breeders simply an irresistible target for brood parasites?  If so, how could hosts repel these cheaters?

Female (left) and male superb fairy-wrens. Image kindly provided by Scott Contini.

Ever vigilant? Female (left) and male superb fairy-wrens.
Image kindly provided by Scott Contini.

Dr. Langmore’s team delved into these questions using a six-year field study in Australia of Horsfield’s bronze-cuckoo (a brood parasite) and one of its cooperative breeder hosts, superb fairy-wrens.  Their observations were striking regarding anti-cheating strategies.  Fairy-wren groups deployed warning calls and brutal attacks against cuckoo females that approached their nests.  Cuckoos rarely breached these perimeter defenses.  In addition, the size of the fairy-wren cooperative group mattered.  “It seems that larger groups are better than small groups at keeping cuckoos away,” notes William Feeney, lead author of the study.  Small fairy-wren cooperatives had a diminished per capita output of chicks simply because cuckoo females were more likely to breach their defenses.

In search of a nest? Horsfield's bronze-cuckoo. Image kindly provided by David Kleinert.

In search of a nest? Horsfield’s bronze-cuckoo.
Image kindly provided by David Kleinert.

These findings imply that cooperative behaviors, particularly on a large scale, are key to forming effective defenses against cheaters.  The field observations do not answer whether cooperative breeding specifically evolved to thwart brood parasites.  But, it appears that the cooperative social structure is a firm foundation for developing cheater repellant strategies.  As Mr. Feeney notes, “When a cooperative breeding species becomes a host of a [brood] parasite, the host should stay cooperative.”  Host groups shrink or disband at their peril.

Cooperation is not the only means to defeat cheaters.  Many mammals and birds deploy complex behaviors that punish cheaters after they strike; some non-cooperative birds, for example, foil brood parasites by abandoning parasitized nests.  But, these strategies might cost the host more compared to cooperative approaches.  These findings from Down Under emphasize the potential efficiency and effectiveness of the social group in stopping cheaters in their tracks.  Though I suppose any kid on the playground could have told you that.

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Passover

A plume of magma may explain North America’s odd geology

At the entrance to the Washington State Fairgrounds in Puyallup. A reminder that I live in the Ring of Fire.

At the entrance to the Washington State Fairgrounds in Puyallup.
A reminder that I live in the Ring of Fire.

Earth’s active geologic processes are a blessing and a curse.  They help sustain life.  Yet, the last sign I saw as I entered the Washington State Fair this summer pointed to an evacuation route in the event of volcanic eruption.  It is no secret most destructive events occur at plate boundaries.  Earth’s crust consists of dozens of tectonic plates moving against one another, causing earthquakes and volcanoes.  But these hazards are much less frequent in the middle of tectonic plates.  In Iowa and the Amazon, you worry more about erosion, not volcanoes.

There are exceptions to this rule, and those exceptions are often caused by hotspots.  Hotspots are regions of volcanic or earthquake activity caused by superheated plumes of magma that rise up from Earth’s mantle.  These plumes melt rock and sometimes pierce the surface, triggering earthquakes and volcanoes.  As a plate moves across a stationary plume, the plume can leave a train of volcanoes in its wake.  The most famous example of these pock-marked scars is the Hawaiian Islands.  The hotspot that created them has punched holes through the Pacific Ocean’s thin oceanic crust since dinosaurs roamed the Earth.

Unlike oceanic crust, continental crust is much thicker, posing a challenge for hotspots that want to be heard.  The particularly violent hotspot beneath Yellowstone National Park has managed to breach thick continental crust several times.  In its last major eruption 640,000 years ago, volcanic debris fell in Mississippi over 1,300 miles away.  But Yellowstone is the exception, not the rule; geologists still struggle to understand just how hotspots behave beneath thick continental crust.  In a paper published last week in Nature Geoscience, a team from the California Institute of Technology report evidence that eastern North America recently passed over a hotspot, with surprising implications for the continent’s geologic history. Continue reading

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The Next Generation

Seattle Center is a 74-acre complex of theaters, music halls, parks, sport facilities, museums, and restaurants tucked neatly within Seattle’s Lower Queen Anne neighborhood.  The iconic Space Needle, crown jewel of the facility since the 1962 World’s Fair, hugs the compound’s southwest corner.  Last June, as part of a celebration of Seattle Center’s fiftieth birthday, the complex hosted the inaugural Seattle Science Festival.  Organized by Seattle’s Pacific Science Center and buoyed by financial support from a number of corporations, businesses, and non-profit organizations from the Puget Sound metropolitan area and beyond, the eight-day festival highlighted research and environmental topics relevant to western Washington’s climate, ecology, and booming science and engineering economy.  The eight-day festival attracted over 40,000 children and families to more than 100 events across the Puget Sound region.

The future.  Now.

The future. Now.

The 2012 festival was so successful that the Pacific Science Center and other major partners decided the event was worth another go.  The second annual Seattle Science Festival began on 6 June and runs through 16 June.  While the majority of the 2013 Seattle Science Festival’s events are held in the Emerald City, dozens of events are scheduled for venues across the Puget Sound metropolitan area, as well as western Washington communities on Whidbey Island, the Olympic Peninsula, and the Cascade foothills.  Saturday, 8 June saw the festival’s signature event: the Science Expo Day.  From 10:00AM to 6:00PM, huge swathes of Seattle Center’s sun-drenched acreage (God bless the dry season) were transformed into roving outdoor science fairs.  The event boasted over 150 booths, staffed by volunteers from dozens of Washington State research institutions, private companies, educational institutions, and non-profit organizations.

Lovely day for science.

Lovely day for science.

I managed to make it over to Science Expo Day for the last 45 minutes of programming to snap photographs and speak with volunteers and attendees.  Even as the evening settled in, the festival’s venue was still packed with families.  Every booth buzzed with activity, and many volunteers rushed to and fro to engage eager children and inquisitive parents alike.  Admittedly, I usually think so-called “family-oriented” outreach events are directed solely toward children, with parents as a mere afterthought.  Yet in nearly every booth, I encountered adults asking as many (if not more) questions than their charges. Continue reading

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Pavane

The solar system’s early days were chaotic.  Our celestial neighborhood began as a rotating cloud of gas and dust.  Some 4.6 billion years ago, the massive center of this cloud condensed into the sun.  Leftover gas and dust, spurred by local gravitational attraction, coalesced to form planetoids.  Over the course of the solar system’s first few million years, these planetary precursors wandered chaotic paths.  Some merged into the first planets, while others were exiled to the solar system’s frigid outback.  But, after 100 million years of wanderlust, this gravitational ballet concluded with eight clear winners: four rocky planets and four gas giants, separated by the Asteroid Belt, and interspersed with comets and dwarf planets.

You are here... somewhere.

You are here… somewhere.

This general model for the solar system’s formation rests on key assumptions about the geologic history of the planets over the past 4.6 billion years.  Many of these assumptions are testable, thanks to humankind’s thirst for space exploration.  In fact, this model has withstood the findings of countless missions to outer space.  But, with chaos reigning in those first 100 million years, today’s solar system still sports peculiarities in need of explanation, and today’s astrophysicists are diving into the details.

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Divining Rod

Another Earth, full of life.  The idea inspires awe and wonder, as well as sober reflection on the savage thrashing we give our own blue oasis.  These notions are fuel for science fiction.  But recent missions have inched Earth-like planets closer to science fact.

The task of identifying another Earth is not trivial.  Planets are not easy to identify.  Though humans have been viewing the night sky for millennia, our own solar system’s full complement was not resolved until the nineteenth century.  The first exoplanet (the term for planets orbiting other stars) was not discovered until 1988, though speculation regarding Earth-like exoplanets quickly followed.

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Leave Them Alone and They’ll Come Home

Humanity leaves a great deal of collateral damage in its wake.  From Fukushima Daiichi to climate change, destruction is often the common denominator of our footprints.  With extinctions on the rise and ecological communities threatened from the Arctic to the Amazon, conservation biologists openly fret that some ecosystems may be too fragile to recover from humanity’s short-sightedness.  But, predicting ecosystem resiliency is about as accurate as reading a crystal ball, thanks largely to the dearth of data on the complex species interactions that define ecosystems.

Coral reefs are particularly complex and delicate marine ecosystems that appear particularly vulnerable to disruption.  As ecological communities go, they have cast their lot in a peculiar spot: the vast but nutrient-poor waters of tropical seas.  Oases in a desert, these reefs shelter fish, algae, seaweed, sponges, crustaceans, mollusks, worms, and starfish, not to mention the corals themselves (odd cousins of anemones and jellyfish).  Reefs form when adult corals aggregate in immobile colonies, clustering on shallow rocks and seabeds.  Their hard calcareous shells protect them and provide a surface on which new corals and other reef creatures can grow and thrive.  Thus, though coral reefs cover less than 0.1% of the ocean’s surface area (all of them could fit inside Nevada), they house over 25% of marine species.
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