Climate Impacts on Ecosystems
Source: http://www.epa.gov/climatechange/impacts-adaptation/ecosystems.html

Climate is an important environmental influence on ecosystems. Climate changes and the impacts of climate change affect ecosystems in a variety of ways. For instance, warming could force species to migrate to higher latitudes or higher elevations where temperatures are more conducive to their survival. Similarly, as sea level rises, saltwater intrusion into a freshwater system may force some key species to relocate or die, thus removing predators or prey that were critical in the existing food chain.

Climate change not only affects ecosystems and species directly, it also interacts with other human stressors such as development. Although some stressors cause only minor impacts when acting alone, their cumulative impact may lead to dramatic ecological changes. [1] For instance, climate change may exacerbate the stress that land development places on fragile coastal areas. Additionally, recently logged forested areas may become vulnerable to erosion if climate change leads to increases in heavy rain storms.


Changes in the Timing of Seasonal Life-Cycle Events
For many species, the climate where they live or spend part of the year influences key stages of their annual life cycle, such as migration, blooming, and mating. As the climate has warmed in recent decades, the timing of these events has changed in some parts of the country. Some examples are:

• Warmer springs have led to earlier nesting for 28 migratory bird species on the East Coast of the United States. [1]
• Northeastern birds that winter in the southern United States are returning north in the spring 13 days earlier than they did in the early 20th century. [4]
• In a California study, 16 out of 23 butterfly species shifted their migration timing and arrived earlier. [4]

How a Few Species Are Hacking Climate Change
Animals can be surprisingly adaptable—but can they change quickly enough?
BYLINE
By Emma Marris, for National Geographic
http://news.nationalgeographic.com/news/2014/05/140506-climate-change-adaptation-evolution-coral-science-butterflies/
PUBLISHED MAY 06, 2014

European larger banded snails (Cepaea nemoralis), such as this one in Italy, with light colored shells are becoming more prevalent over time in the Netherlands.
PHOTOGRAPH BY FRANCESCO TOMASINELLI, VISUALS UNLIMITED/CORBIS

As the Earth heats up, animals and plants are not necessarily helpless. They can move to cooler climes; they can stay put and adapt as individuals to their warmer environment, and they can even adapt as a species, by evolving.

The big question is, will they be able to do any of that quickly enough? Most researchers believe that climate change is happening too fast for many species to keep up. (Related: "Rain Forest Plants Race to Outrun Global Warming.")

But in recent weeks, the general gloom has been pierced by two rays of hope: Reports have come in of unexpected adaptive ability in endangered butterflies in California and in corals in the Pacific.
Two isolated reports don't, of course, diminish the gravity of the global threat. But they do highlight how little we still know about nature's ability to cope with climate change.

"Most of the models that ecologists are putting out are assuming that there's no adaptive capacity. And that's silly," says Ary Hoffmann, a geneticist at the University of Melbourne in Australia and the co-author of an influential review of climate change-related evolution. "Organisms are not static."

Nature on the Move
That species are on the move is becoming obvious not just to scientists but also to gardeners and nature-lovers everywhere. Butterflies are living higher up on mountains; trees are moving north in North America and Europe. In North Carolina, residents are still agog at encountering nine-banded armadillos, which have invaded the state from the south.

A 2011 review of data on hundreds of moving species found a median shift to higher altitudes of 36 feet (11 meters) per decade and a median shift to higher latitudes of about 10.5 miles (17 kilometers) per decade.

There's also a clear warming-related trend in the timing of natural events. One study suggests that spring shifted 1.7 days earlier between 1954 and 2007. Insects are emerging earlier; birds are nesting earlier; plants are flowering and leafing out earlier. The latest of such natural events studies, out last month, shows that climate change has stretched out the wildflower bloom season in Colorado by 35 days.

The report last month from a butterfly conference in England was a bit different, however. It concerned the endangered quino checkerspot butterfly (Euphydryas editha quino), well known for being threatened by climate change. Many experts believed the species was doomed unless humans collected the butterflies and moved them north; their path to higher ground seemed to be blocked by the megalopolis of Los Angeles.

But at the conference, according to an account in the Guardian, Camille Parmesan of the Marine Sciences Institute at Plymouth University in the U.K., who has studied the quino checkerspot for years, reported that it had miraculously shifted its range to higher altitudes. Furthermore, it had somehow learned to lay its eggs on a new host plant.

"Every butterfly biologist who knew anything about the quino in the mid-1990s thought it would be extinct by now, including me," Parmesan told the Guardian. (Parmesan confirmed the account for National Geographic, but declined to elaborate until she could publish her own research paper on the subject.)

Resilience in Corals
Another uplifting tale of unexpected resilience appeared in Science on April 24. While surveying the waters of the future National Park of American Samoa off Ofu Island, researcher Peter Craig noticed isolated coral pools that were considerably warmer than the rest. High water temperatures can cause corals to "bleach": They spit out the photosynthesizing algae that live inside them, thereby losing both their color and their means of collecting energy. Yet these particular corals didn't seem to be suffering too much from the heat.

Marine ecologist Stephen Palumbi of Stanford University in California tested the heat tolerance of some of the Acropora hyacinthus corals from unusually hot pools. He plopped them into a container, then cranked up the heat inside to 34 degrees Celsius (93 degrees Fahrenheit) for three hours. Just 20 percent of the individual coral animals spit out their algae, whereas 55 percent of coral from an otherwise similar but much cooler pool spit out their algae during the test.

The more revealing test came next. Palumbi took corals from the cool pool and put them in the hot pool. One year later, he measured their heat tolerance—and found it had greatly improved. The heat stress test caused only 32.5 percent of the transplanted corals to spit out their algae, instead of 55 percent.

Palumbi's experiment helped tease out the two different mechanisms by which organisms can adapt. Individual transplanted corals were able to adapt to the hotter water, without any change in their genes. Biologists call that phenotypic plasticity.

But the transplanted corals were still not as good at taking the heat as corals that were native to the hot pools; 32.5 percent of them bleached during the stress test, compared with just 20 percent of the hot-pool natives. That gap might reflect the operation of another mechanism of adaptation: genetic evolution. Over many generations, natural selection may have changed the genes of corals in the hot pools by allowing the most heat-tolerant ones to survive and produce more offspring.

For the Samoan corals in a warming ocean, the combination of plastic adaptation and genetic evolution could be "the difference between dead and more or less unfazed," Palumbi says. The results suggest to him that previous predictions of extinction for all coral might be a bit too pessimistic.

More generally, such individual stories of adaptive ability suggest that the quality of resilience has been left out of our models and predictions about how the natural world will respond to climate change. "I do think there is more hidden adaptability out there," says Palumbi.

Snails, Salmon, Owls, and Thyme
So far, evidence of adaptability is available for only a few species. Juha Merilä of the University of Helsinki in Finland, who edited a special issue of the journal Evolutionary Applications in January rounding up the evidence for such changes, guesses that there are perhaps 20 studies robustly linking adaptation through phenotypic plasticity to climate change, and another 20 or so clearly linking climate change with genetic evolution. But, he says, it's likely that this is a tiny fraction of the species in which adaptation is occurring.

There are better data on shifts in ranges and the timing of events, thanks in part to citizen science efforts like Project Budburst and the Great Backyard Bird Count. But these studies don't prove whether the shifts are due to plasticity or genes, or even that climate change is the underlying cause—they're just highly suggestive correlations between rising temperatures and the location and behavior of species.

Among the most solid examples of actual evolution in response to climate change is a shift in the proportion of European larger banded snails (Cepaea nemoralis) with light colored shells. Shell color is genetic, and the genes responsible are known. It has been shown that, in a given environment, snails with light colored shells have a lower body temperature than those with dark colored shells. And light colored shells are becoming more prevalent over time in the Netherlands, even in wooded, shady environments where you might expect dark shells to dominate.

A few other studies have caught species actually evolving in response to climate change. Pink salmon in Auke Creek, Alaska, which is heating up .03 degrees Celsius (.054 degrees Fahrenheit) per year, are now migrating out of the creek earlier, and scientists have shown that that change is genetic.

Wild thyme (Thymus vulgaris) in France has evolved in response to fewer extreme cold events since the 1970s, producing more pungent oils to deter herbivores (at the cost of becoming less cold-hardy).

Tawny owls (Strix aluco) can be light gray or brown, depending on the genes they inherit from their parents. As snow cover in Finland has declined since the late 1970s, the light gray owls, best camouflaged during snow, no longer have much of an advantage, and scientists have shown that brown owls are now much more common.

Such studies require patience. "It is really hard to get the evidence because you need long-term studies and it is very hard to make science over these kinds of periods," says Merilä. The snails have been studied for at least 45 years, the owls for 36, and the salmon for 32.

And such studies also leave unresolved how one ought to feel about these subtle transformations. When we see spring springing earlier or snails changing color, should we mourn the changes as sad, human-caused degradation, or embrace them as evidence of plucky nature fighting back? "A bit of both," says Hoffmann. "We have to accept that things will change."

"I think we should feel impressed by the impact that we have, that we can change the course of evolution around us by the way we change the environment," says Menno Schilthuizen, who studies how invertebrates adapt to climate change at the Naturalis Biodiversity Center in Leiden, Netherlands. "Our impact is much further and deeper than we tend to think."

Some Will Die
Researchers on this topic are quick to point out that evolution and individual plasticity won't save all species. Climate change is happening too fast, they say, for some species to survive.

Hypotheses abound on which species are likely to keep up with climate change. Species with short lives, like fruit flies, have more generations in which to evolve, compared with long-lived species that don't begin to breed for decades. And some species, like some conifer trees, simply have more gene variants to work with in their populations.

Conversely, long-lived species with low genetic variability—including many rare mammals—will have less adaptive ability. "In general, you might expect that weedy, short-lived species and ones that are able to disperse widely might be favored," says Steven Franks, who studies how plants adapt to climate change at Fordham University in New York.

There's also a widespread but still poorly tested hypothesis that tropical species may have a harder time evolving than temperate species do. Having evolved in a region with less climate variability over both the years and the millennia, tropical species may harbor a less diverse set of genes related to heat tolerance and similar traits. "The tropics are hot, but they are not particularly variable," Hoffmann says. "It is not like they are being challenged all the time."

Predicting which species will survive on their own can help researchers zero in on which species might benefit most from human help. A key goal of such an intervention would be to bring back genetic diversity to small, isolated populations so that evolution has something to work with. "Where we have a fragmented landscape, we should connect it up again, restore the flow," says Hoffmann. "We are restoring a process, and that process is really powerful."

Where it's not possible to connect fragmented populations with contiguous habitat, "restoring the flow" could mean moving seeds or individuals from population to population. In dire cases, Hoffmann says, conservationists might want to create hybrids of two related species or subspecies, if each one is insufficiently able to adapt on its own. "People think 'genetic pollution!'" he says. "But you could achieve a lot in terms of saving these populations."

Palumbi, meanwhile, thinks the adaptability he found in Samoan corals won't save them as much as provide a grace period; eventually, he says, human-made climate change could outstrip the corals'—and many other species'—ability to adapt.

"That delay of a couple of decades is the good news here," he says. "Let's use the decades to solve the problem." And when he says "the problem," he means the root of the problem: carbon emissions.

Life Makes a Mark
Source: American Museum of Natural History
http://www.amnh.org/explore/science-bulletins/earth/documentaries/the-rise-of-oxygen/article-life-makes-a-mark

Consider the forces that have shaped planet Earth over time, and one tends to picture the grand geophysical events: earthquakes and volcanoes, erosion by wind and water, the drift of continental plates, the warming and cooling of the global climate. But there is another crucial force, microscopic in size yet global in its impact: the microbe.

Single-celled microscopic organisms—microbes—are the oldest and most abundant form of life on Earth. The term "microbes" spans a bewildering range of life-forms, from plants to animals to the ambiguously classified fungi. And microbes occupy an astonishing range of habitats, from the familiar (your shower curtain) to the most forbidding (inside volcanoes on the seafloor). In 1683, Antoni van Leeuwenhoek, the first scientist to view living bacteria through a microscope, exclaimed: "There are more animals living in the scum on the teeth in a man'­s mouth than there are men in a whole kingdom."

Since their first emergence on Earth perhaps more than 3.8 billion years ago, microbes have dramatically altered the chemistry of the atmosphere and, with it, the planet'­s surface. Among the countless kinds of microbes that have evolved, none have quite equaled the accomplishments of the first cyanobacteria (the stromatolites in Glacier National Park in Montana and in the Mission Mountains were formed by stromatolites). These organisms were photosynthetic organisms that, like plants, drew on the Sun'­s energy to create oxygen, and in doing so helped create an oxygen-rich atmosphere. Earth today is habitable to multicellular creatures like us largely because cyanobacteria made it so. "One cannot separate the study of Earth'­s early atmosphere from the study of the evolution of life on this planet," says Jay Kaufman, a geoscientist at the University of Maryland. "They are intimately linked."

Wherever they may live, microbes thrive on basic chemistry. Think of them as molecular scrap-metal workers: They take apart commonplace chemical compounds and reassemble the individual parts, or ions, into altogether different molecules. For example, phytoplankton, microscopic plants that flourish near the ocean surface, convert carbon dioxide (CO2) and water (H2O) into carbohydrates and oxygen (O2). Though small in size, these microbes are so abundant that they generate half the oxygen we breathe.

What does a microbe earn for its labors? An infusion of energy, gained through the handling of miniscule, negatively charged particles called electrons. Every atom is surrounded by electrons, which help bind atoms together into molecules. As molecules are broken down and reformed, their electrons are exchanged and redistributed. A microbe, in the course of reshuffling ions and molecules, siphons off an electron or two for itself, to be used later in still other chemical reactions in its pursuit of food and energy. The molecules it generates, meanwhile, can become fodder for all sorts of other microbes. Leeuwenhoek was right: dental plaque is in fact an assembly line involving several species of bacteria, each playing a different role in the conversion of sugars and carbohydrates into cavity-causing acids. Your teeth are the platform for an entire atomic economy that runs on a currency of electrons.

Through eons of evolution, microbes have adopted impressive strategies to exploit and metabolize the many kinds of molecules that exist on Earth. The bacterium Pyrococcus furiosus thrives in the hot water that boils from undersea volcanic vents. This heat-loving microbe doesn'­t breathe oxygen; in fact, oxygen is toxic to it. Instead it takes in sulfur and releases hydrogen sulfide, the same gas that makes rotten eggs stink. This hydrogen sulfide is part of a bizarre seafloor food chain that never sees sunlight and includes creatures like albino clams and tubeworms.

A scrap-metal business thrives, or doesn'­t, depending on the availability of certain prized metal parts. So too with microbes. Oxygen-breathing organisms—microbes as well as larger, multicellular creatures like us—abound today only because there'­s plenty of atmospheric oxygen to breathe. Before about 2.4 billion years ago, when there was no atmospheric oxygen, different organisms, all of them microbial, dominated Earth. The sulfur-breathing bacterium P. furiosus is a descendant of the oldest branch of life, the Archaea, which some scientists believe may date back to that early oxygen-less era. Today, many Archaean microbes are relegated to murky, oxygen-free corners of the planet, including seafloor volcanoes and the intestines of cows.

Whatever a microbe produces—oxygen, methane, hydrogen sulfide—the task does require some effort, and the microbe must derive the initial energy to perform it from somewhere. Many scientists think that the earliest microbes derived their energy indirectly from Earth'­s internal heat, much as P. furiosus does today. Photosynthesis, the ability to convert the Sun'­s energy into microbial labor, developed somewhat later, perhaps as early as 3.5 billion years ago.

Photosynthesis was a major evolutionary invention, as it freed organisms from the ocean depths and enabled them to thrive just below the sea surface. But the greatest innovation was yet to come. Photosynthetic microbes, though able to utilize solar energy, were still restricted to the shallows; ultraviolet radiation from the Sun was so strong that nothing could live exposed on land. Then, around 2.7 billion years ago, a class of organisms called cyanobacteria appeared. Unlike their other photosynthetic cousins, these photosynthetic microbes produced oxygen. (To learn about the fossil evidence for cyanobacteria, watch the accompanying video "Early Fossil Life.")

The appearance of cyanobacteria signaled the beginning of a global transformation. Free oxygen began to accumulate in the atmosphere, forming two gases new to Earth. One was molecular oxygen (O2), well known to those of us who breathe it. The other was ozone (O3), a gas that forms high in Earth'­s atmosphere and, acting as a sort of global sunscreen, shields Earth'­s surface from the most harmful UV radiation. In the long run, the gradual rise of oxygen had two sensational effects: It permitted life to evolve on dry land, and it permitted the evolution of organisms that could thrive on oxygen. You can breathe easily, thanks to those early cyanobacteria.

"Imagine an early Earth that had no global sunscreen, no oxygen, hence no ozone," says Kaufman. "The production of oxygen through photosynthesis created that sunscreen. So biology actually made the surface environments habitable for future life by producing the oxygen we breathe today."

The role of microbes didn'­t end 2.4 billion years ago. Microscopic organisms are equally prevalent today, although they tend not to draw the same media attention that flashier, multicellular creatures do. And they'­re still churning out free oxygen, replenishing atmospheric O2 as quickly as other animals and chemical processes use it up. Like an earthquake or volcano, the lowly microbe is a planetary force to be reckoned with and respected.

"The atmosphere we have today is strongly influenced by biological activity," says Kaufman'­s colleague James Farquhar, a geochemist at the University of Maryland. "It'­s influenced by the types of gases that bacteria and other organisms produce. Life is critical in determining atmospheric composition, just as atmospheric composition is critical in controlling the conditions that are required to allow life to exist as it does."