With the political debate heating up over the American Clean Energy and Security Act, it's easy to lose sight of what the fight is about.

Yes, this is about people and jobs and freeing ourselves from foreign oil and creating a clean energy economy for the 21st century. But it's also about our natural heritage and the wildlife with which we share this planet.

Species from blue whales to butterflies confront growing threats. Their habitats are rapidly changing along with the climate. Global warming is pushing nature to the brink.

That's why we launched a new campaign, Warming and Wildlife, where we document the story through the prism of seven "ambassador species" from across America already struggling to survive.

Without action, there's a good chance these species won't make it – we could lose them in our lifetimes.

Our seven ambassador species are:

• Sugar maple
• Monarch butterfly
• Leatherback sea turtle
• American pika
• Canada lynx
• Tufted puffin
• Polar bear

The bumper sticker is right: Extinction is forever. But, it doesn't have to be inevitable, not if we each do our part to cap America's global warming pollution and unleash the clean energy economy of the 21st century.

But new research shows that old-growth forests are even more important than previously thought. According to a new study in Nature, old-growth forests aren’t just standing there maintaining the status quo. They still actively take up CO₂ from the atmosphere.

The dominant trees in old-growth forests are about as big as they're going to get. So for a long time, scientists thought that old-growth forests were carbon neutral – that the plants took up as much CO₂ from the atmosphere as was released from plant and soil respiration. (To learn about respiration, see Bill's post on agricultural offsets.)

To check this assumption, researchers compiled data from 519 studies that reported one or more components of the carbon cycle. Because data for tropical forests was scant, the study included only boreal (northern) and temperate forests.

Their analysis showed that even centuries-old forests are active carbon sinks – they take up more CO₂ than they release. In fact, old-growth forests in temperate and boreal zones take up as much as 1.3 gigatons of carbon (Gt C) a year. To put that in perspective, that's approximately 17 percent of global fossil fuel CO₂ emissions in 2005.

It's been estimated that deforestation accounts for 20 percent of current global greenhouse gas emissions. This study adds to the urgency of protecting forests. As the study's authors put it:

The present paper shows that old-growth forests are usually carbon sinks. Because old-growth forests steadily accumulate carbon for centuries, they contain vast quantities of it. They will lose much of this carbon to the atmosphere if they are disturbed, so carbon-accounting rules for forests should give credit for leaving old-growth forest intact.

We agree! EDF's market-based plan to give credit for leaving forests intact is called Compensated Reduction (CR), and we're working hard to make this a reality. EDF is an active participant in the international negotiation towards a post-Kyoto agreement. We're pleased that deforestation was a major topic at the Bali talks, and the more recent talks in Accra, Ghana, as well.

This post is by Lisa Moore, Ph.D., a scientist in the Climate and Air program at Environmental Defense Fund.

Earth is home to millions of species. This rich biodiversity isn't just beautiful, it's also tremendously valuable. As just one example, consider coral reefs. They support fisheries that are the main source of protein for a billion people, and bring billions of tourist dollars into local economies.

Scientists have warned that climate change puts a large fraction of Earth's species at risk for extinction. Most of these predictions are based on comparisons between species' apparent climate requirements to projections of future conditions. A new study [PDF] in the Proceedings of the Royal Society B looks at the relationship between climate and biodiversity from a different perspective: the Earth's deep past. The study found a long-term correlation between global temperature and extinction.

Biodiversity has increased in the billions of years of Earth's history, but there have been ups and downs along the way. To find out if climate has anything to do with this variation the scientists compiled records of global temperature and biodiversity over the past 520 million years. They looked at biodiversity at the family level – for example, looking at the sunflower family rather than its 24,000 species. Then they looked at correlations between temperature and three aspects of biodiversity: "standing diversity" (the number of families present at any one time), the rate at which families appeared over time, and the rate at which families went extinct.

There were many interesting patterns, but the result that has received the most attention was that extinction rates tend to be higher during warm periods than cool periods. What does that mean for today's global warming?

You can't translate these results into short-term predictions because this study used time steps of 10 million years. That's hugely different from the decadal time scales that apply to today's rapid global warming! The authors make that (and other caveats) very clear in the paper. And, like all scientific studies, this one raised a lot of fascinating questions that need further investigation.

On the other hand, even with all the caveats and questions, this study provides little reassurance for the species and ecosystems we love and depend on. As one of the authors said, "If our results hold for current warming – the magnitude of which is comparable with the long-term fluctuations in the Earth's climate – they suggest that extinctions will increase."

This week I came across several interesting articles related to climate, but two in particular caught my eye. In the first, scientists found that excess carbon dioxide (CO₂) may be what's leaving livestock with less food to eat. The other study explores the role of greenhouse gases on the record-breaking heat Americans experienced in 2006.

Morgan, et al. 2007. Carbon dioxide enrichment alters plant community structure and accelerates shrub growth in the shortgrass steppe. Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0703427104.

For decades, woody shrubs have been replacing grasses in parts of the western U.S. This is a serious problem for ranchers because, as shrubs encroach into grazing lands, livestock have less food to eat. This new study from the U.S. Department of Agriculture suggests that CO₂ may be a culprit, because prairie sagebrush is extremely sensitive to CO₂ levels. In a five-year experiment in Colorado's shortgrass steppe, sagebrush cover increased twenty-fold in areas that were exposed to higher CO₂ levels.

Hoerling, et al. 2007. Explaining the record US warmth of 2006. Geophysical Research Letters 34: L17704.

Last year, the U.S. experienced record-breaking temperatures and deadly summer heat waves. Did global warming play a role? This study, by scientists at the National Oceanic and Atmospheric Administration, found that El Niño had little influence on U.S. temperatures. Instead, the researchers found that the greenhouse effect is now stronger than natural temperature variations. They concluded that "the record warmth was primarily due to human influences".

Last weekend's Mercury News ran a news story about vehicle emissions harming native species in California. The excess nitrogen from vehicle emissions caused invasive species to displace the plants that feed the bay checkerspot butterfly, which is threatened with extinction. My friend and colleague Dr. Stuart Weiss, the scientist who uncovered the link, calls this "drive-by extinction".

Nitrogen pollution has profound effects on life, health, and climate, yet these go mostly unnoticed by policymakers and the public.

Nitrogen and Ecosystems

Burning fossil fuels releases nitrogen oxides – compounds of nitrogen and oxygen that are collectively known as "NOx". Rain washes nitrogen from the atmosphere, but it also can settle to the ground in dry form. Scientists call this "nitrogen deposition".

Nitrogen's ecological impact is large because it's essential for life but scarce. Until people started burning fossil fuels and using fertilizer, the nitrogen cycle was ruled by soil bacteria, which pull nitrogen from the atmosphere and make it available to plants, and respire it back into the atmosphere. Species and ecosystems evolved to function on the small amount of nitrogen that was available.

Human-caused nitrogen deposition has greatly increased the amount of nitrogen added to the Earth's surface each year, with wide-ranging impacts. (See the "The Nitrogen Cascade [PDF]" for a good overview.) Some plants are more sensitive to nitrogen than others, and the species that grow more can displace other species. Unfortunately for the bay checkerspot butterfly, the displaced species was its main food source. And it's not the only casualty. In his report "Impacts of Nitrogen Deposition on California Ecosystems and Biodiversity [PDF - 7MB]", Dr. Weiss shows that hundreds of California's rare plant and animal species live in deposition hotspots.

Nitrogen and Public Health

The NOx emitted from tailpipes and smokestacks also damages health. Environmental Defense has put together a fact sheet outlining the problem [PDF], and an in-depth look at the problem in New York City [large PDF].

The damage comes from multiple directions. The NOx gas nitrogen dioxide (NO₂) is a lung irritant that also increases susceptibility to infection. Plus, NOx gases combine with ammonia in the atmosphere to form ammonium nitrate – an important component of fine particulate matter that inflames blood vessels and increases the risk of heart attack and stroke. And that's not all. NOx gases are precursors to ground-level ozone (smog), a lung irritant that aggravates asthma, and can cause premature death.

Nitrogen and Climate

As I explained in my post "Ozone Alert For Plants", the same chemical reactions that form unhealthy smog also increase levels of tropospheric ozone, a greenhouse gas. So nitrogen contributes to global warming in that way – but that's not all.

Use of fertilizers is another major source of nitrogen. Producing synthetic fertilizer is energy intensive, and so produces greenhouse gases. Plus, only a fraction of the nitrogen supplied by the fertilizer will be taken up by crops. Some of what's wasted is washed into streams where it contaminates drinking water and causes coastal dead zones. Soil bacteria convert the remainder into gas – including the highly potent greenhouse gas nitrous oxide – which escapes back to the atmosphere.

What Can We Do?

We have the technology to cut NOx emissions from power plants – we just need to do it. Measures to reduce traffic congestion also can make a big difference. Farmers can decrease the amount of fertilizer they use, without affecting crop yields. A study in Mexico found that farmers could decrease nitrous oxide emissions 95 percent, using 28 percent less fertilizer, just by changing when they added it to their fields. Environmental Defense is working with farmers in the Mid-Atlantic and Midwest to use fertilizers more efficiently.

Nitrous oxide is a large slice of the greenhouse gas pie, so we need to pay attention to it. And as the bay checkerspot butterfly reminds us, cutting nitrogen pollution for the climate's sake will bring many other benefits.

If you're in or near a big city, you've probably heard your local news give ozone alerts. Those warnings mean that smog levels are high enough to affect your lungs. Even moderate pollution causes respiratory problems for kids with asthma. Really high levels of ozone make it dangerous for even the healthiest adult to be outdoors.

Now scientists are warning that smog could make global warming worse because of its effects on plants.

It turns out that ozone not only hurts your lungs, it also decreases plants' ability to take up carbon dioxide (CO₂). That's a problem – plants remove heat-trapping CO₂ from the atmosphere – but how much of a problem? Is it enough to affect global climate?

Scientists have studied the effects of elevated CO₂ and ozone on plants for years. Researchers expose leaves, plants, or whole ecosystems to combinations of elevated CO₂ and ozone and measure the plants' responses over time. But these are small-scale experiments.

A few weeks ago, researchers led by Dr. Stephen Sitch published a paper in Nature titled "Indirect radiative forcing of climate change through ozone effects on the land-carbon sink [PDF]" (paid subscription required) that attempts to quantify the problem on a global scale. Using data from the small-scale experiments, they modified a global-scale carbon cycle model to include the effects of CO₂ and ozone on plant CO₂ uptake. (See my previous post for more on how climate models work.) Then they ran the model using a business-as-usual scenario of CO₂ emissions, with and without projected increases in ozone concentration.

The results were striking. In all cases, plants continued to take up extra carbon, but when the effects of ozone were included, they took up significantly smaller amounts. In other words, as smog increased, the rate at which CO₂ accumulated in the atmosphere also increased. The upshot is that ground-level ozone does seems to add to global warming.

The same chemical reactions that produce smog also increase ozone in the upper troposphere, where it acts as a greenhouse gas. The authors estimate that the indirect warming effects of ozone through its effects on plants could be as large as the direct warming impact of ozone in the upper troposphere. (Ozone is also found in the stratosphere. See Bill's post on "Global Warming and the Ozone Hole".)

So the bad news is that smog could exacerbate global warming. The good news is that existing pollution controls can lead to rapid air quality improvements, meaning less smog and less global warming.

Last week, Bill summarized two new studies about carbon dioxide levels in the atmosphere and ocean. This week brought three very different topics: hurricanes (quite timely, since today is the first day of the Atlantic hurricane season!), global rainfall patterns and rainbow trout.

• There is a lively scientific discussion going on about the effects of global warming on hurricanes (see Wednesday’s post). A new study published in Nature added a new twist: global warming and hurricanes might interact to make global warming worse.

• Global warming increases both evaporation and rainfall. In a paper released through Science Express, scientists showed that climate models were spot-on in predicting evaporation but underestimated rainfall. This is a great dataset to help scientists fine-tune the models. It also suggests that future rainfall could be higher in some areas than scientists have projected. Unfortunately, this does not dismiss concerns of drought in other areas. (Learn more here.)

• And the last item on today’s menu: rainbow trout. In a paper published in the Proceedings of the National Academy of Sciences, researchers described fish behavior and survival rates in several lakes. In warmer years, rainbow trout survival declined as much as 50 percent. The reason: as water warms, metabolism increases, so fish need to eat more – and that can put fish in harm’s way. Hungry young trout expose themselves to predators more often.

Want more details on any of these studies? Let me know and I’ll try to do a post on it.

1. More Acidic Oceans
2. Drinking Water and Disease
3. Shifts in Lifecycle Timing
4. Drought and Violence
5. Melting of the North Pole

Spring is finally here, and lifecycles are on display all around us — flowers are blooming, birds are migrating, eggs are hatching. The signs of spring may seem simple, but actually they're intricately choreographed. Flowers bloom when insects are around to pollinate them; migrating birds and newborns normally arrive when there is food for them to eat. Life's fragile choreography is based on signals from the environment, such as light or warmth. As global temperatures rise, what happens to all those cues?

One of the most obvious effects of global warming is that spring is starting earlier. Frogs are calling earlier. Birds are migrating and breeding earlier. Butterflies are emerging earlier. All good things, right?

Unfortunately, not all plants and animals are flexible enough to take part in the early spring. Scientists are finding that as temperature cues change, some species are getting out of sync others, disrupting the coordination necessary for survival. There are already documented cases:

A cute little European bird called the pied flycatcher depends on caterpillars to feed its chicks. Over the past 20 years, as temperatures have risen, caterpillars have emerged earlier and earlier, but the flycatchers' egg-laying dates have not advanced as much as the caterpillars. When chicks hatch after the caterpillar population has peaked, adult birds can't find enough food to feed their young. In some areas, flycatcher numbers have plummeted 90 percent [1]. (We also have to wonder about the consequences of all those caterpillars that are no longer bird food.)

The flycatcher's story is fairly well known, but there are other examples, too:

• In Europe and North America, migrating birds such as swans, buzzards, warblers and robins are arriving at their feeding and breeding grounds earlier, which is not always the same time their food sources are available [2].
• In the ocean, different parts of the marine food chain are getting out of sync [3].
• In Colorado, yellow-bellied marmots emerge from hibernation three weeks earlier than they did 30 years ago, but the plants they eat haven’t changed their timing [4].
• In California, the rare bay checkerspot butterfly has started mistiming its emergence date relative to its host plants [4].

Today's rapid global warming is disrupting the delicate timing that evolved over thousands of generations. Some species are adapting; others are clearly in trouble. How will these changes filter up the food chain to our food supply? Hard to say, but it could be surprising and unpleasant. Consider what is now happening to bee colonies. For reasons that are not yet understood, bees are disappearing throughout the United States (registration required). Unfortunate but no big deal, you think? Well, it is a big deal because we depend on bees to pollinate the crops we eat. Their disappearance may undermine our food production system.

There is no evidence that global warming is implicated in the bee disappearance, but the phenomenon reminds us that we are critically dependent on the services provided by species and ecosystems. The fact is that global warming is upsetting ecosystems in both subtle and profound ways. We allow these warming trends to continue unabated at our own risk.

References
1 Christiaan Both et al., published in Nature.
2 Marcel Visser and Christiaan Both, published in Proceedings of the Royal Society.
3 Martin Edwards and Anthony Richardson, published in Nature [PDF]
4 Camille Parmesan, published in Annual Review of Ecology, Evolution, and Systematics [PDF]