Winter is over. Can spring be far away?

Even before the lunar new year, cherry trees and rhododendrons were blooming on Taipei's Yangming Mountains, around Wushe in Nantou County, and at Wutai in Pingtung-the flowering season had arrived early. Early enough, in fact, to compete with "autumn colors": in late December, smiling travel agents in Taichung were still busily signing people up for tours to Auwanta to admire the red-leafed sweetgum trees. Earlier still, in November, along the mountain roads of Wulai Rural Township in Taipei County the blossoming tung trees formed an entrancing swathe of white. Usually, they do not flower until April or May. But at Fengkuitou in Nantou's Hsinyi Rural Township, where the plum trees normally all burst into bloom at once around mid-January, the breathtaking sea of white was nowhere to be seen, for this winter there was no continuous cold period to synchronize the trees' flowering. However, Huang Chih-hui, general secretary of Hsinyi Farmers' Association, says with glee that as the trees did not flower in unison, the blossom-viewing period was longer than usual, and this allowed local traders to do more business.

Blooming crazy

This disruption of spring flowering patterns was good news for some, but bad news for others. The prospect of cash crops not making it to market on time is a big worry for farmers. In Taoyuan County in late September, the poinsettias, which should have been turning red, were still stubbornly green in their pots. With Christmas approaching, the flower farmers turned to the district agricultural improvement station for help. The growth of cold-loving plants such as pocketbook and cineraria also faltered, forcing floriculturists to install water sprays and fans to cool the plants until they resumed their normal pace of growth.

In fact it is not unusual for a change of seasons to occasionally come early or late and upset the sequence of nature, and it is quite common for plants to be fooled by the weather. In ancient times farmers were aware that "if a fruit tree that normally flowers in spring blossoms in autumn, it will not set fruit." But disruptions of plants' growth cycles seem to be becoming ever more frequent, and when everything from wild plants to coastal algae to farm crops starts acting strangely, it convinces people that the greenhouse effect is quietly plucking at the sensitive nerves of Mother Earth, and changing the pattern of nature.

That is why the warm winter has generated so much comment. But views in the scientific community are divided, with many researchers remaining skeptical. Hung Fu-jen, deputy director of the Taiwan Forestry Research Institute, says that if the broadleaved forests that grow in Taiwan at elevations below 1000 meters, or the firs at 2000 meters, were to gradually move towards higher elevations, producing distinct changes in the positions of different vegetation zones, then climate warming would certainly be a prime suspect; but this requires long-term observation. "Long-term environmental research in Taiwan has been going on now for a decade, but thus far it is very difficult to reach conclusions," says Hung.

Long-term trends

In recent years there have also been unusual patterns in the growth of seaweed alongside Taiwan's coasts. Some people suspect that this is connected with rising sea temperatures. But algae researcher Wu Chun-tsung, a research fellow at Academia Sinica's Institute of Botany, takes a more cautious attitude, saying that manmade pollution is probably a greater factor than climate in causing changes in the distribution of coastal macroalgae. But he stresses that all the world's different organisms have different characteristics, and therefore have different sensitivities and reactions to climate change. A long-term temperature rise of one or two degrees Celsius is unlikely to have much impact on large animals in the short term. "On the evolutionary level, humans have a greater level of tolerance. But small animals, and organisms that depend on specific weather, temperature and humidity conditions, will be more sensitive," says Wu.

"The effects of climate change show up much more quickly in fish than in other animals," says Professor Lee Kuo-tien, dean of academic affairs at National Taiwan Ocean University. But fish cannot speak, and in the water they suffer the effects of warming in silence. "By the time humans are sure the Earth has caught a fever, the fish may all be dead!" says Lee.

In recent years, the people who have most systematically studied the effects of climate change on living creatures are probably fisheries researchers.

Cold fish

"Mullet prefer cold water!" is a fact of fish behavior well known to fishermen. In December each year, around the winter solstice, many fishing boats begin to gather on the waters southwest of Taiwan, hoping for cold weather. Mullet mature in the seas off mainland China, and in winter, when bodies of cold coastal water move south, the mullet shoals go with the flow, swimming down past the mouth of the Yangtze River. At the same time, to the south of Taiwan, warm water branching off from the Kuroshio Current (the main part of which flows north along Taiwan's east coast) runs up against the cold mainland water southwest of the island, barring its southward path. Under the sea off Yunlin and Chiayi, another factor also comes into play: the sea floor rises to form the Yunlin-Changhua Ridge, which blocks out the waves of the East China Sea and the Taiwan Strait. This creates a sheltered area southwest of Taiwan that is an excellent spawning ground for mullet, and supports several large fishing harbors.

In the 1980s, Taiwan's annual mullet catches reached record levels of over 2.5 million fish. But subsequently they dropped dramatically year by year, and in recent times they have fallen to less than 200,000. Satellite studies by NTOU have shown that apart from overfishing by fishermen from both sides of the Taiwan Strait, another reason for the drastic decline in mullet numbers is that due to climate warming, the cold mainland waters are no longer moving far enough south.

In particular, in the El Nino years of 1997 to 1999, shifts in ocean currents pushed the warm water of the Kuroshio Current further into the Taiwan Strait, past Chiayi and Yunlin, blocking the southward movement of the cold waters from the mainland coast. The water temperature in the mullets' former spawning grounds rose, and the southward-swimming mullet shoals stopped short of them. But the fish had to spawn somewhere, so some turned west towards Kinmen, while others went east into the Pacific waters off Ilan County, bringing fishermen there unexpected windfall catches.

Ocean thermometer

Through satellite observations, the fishing industry has gradually come to understand the waxing and waning of cold and warm currents. Noting the succession of warm winters in the 1990s, and a 1°C rise in sea temperatures around Taiwan, the Taiwan Fisheries Research Institute also began making fish catch forecasts based on sea temperatures. For instance, the temperature that best suits mullet is 21-23°C, but last year the institute predicted that sea temperatures around southern Taiwan would be 2-3°C warmer this winter than in previous years. Sure enough, the mullet catch was a far cry from the golden days of mullet fishing, and the quantity and quality of mullet roe production was badly hit.

Apart from this, in recent years production of elvers and anchovies, previously important foreign exchange earners for Taiwan, has fallen, seed oysters have set late, and the shoals of mackerel and jack that formerly provided the largest catches in inshore waters have disappeared. Fishermen have connected all these phenomena with warm winters.

Not only have coastal fish species' life cycles been turned upside down: the deep-sea fishing industry is also affected by climate change. Assistant Professor Lu Hsueh-jung of the fisheries science department at NTOU points out that tuna and squid, which provide the two largest catches for Taiwan's deep sea fishing industry, are both highly sensitive to changes in ocean currents and water temperature. They too always "follow the water temperature."

Over the past three years, Lu Hsueh-jung has been surveying changes in the distribution in Pacific waters of the three types of tuna that make up the bulk of Taiwan's tuna catch: albacore, yellowfin and skipjack. For skipjack, Taiwanese boats mainly work the central and west Pacific. Lu discovered that in ordinary years, when warm water is concentrated in a pool in the West Pacific, this area is the main habitat of skipjack tuna. But during an El Nino event the pool of warm water moves east almost all the way across the Pacific, and the tuna, following the rich source of food and energy that the warm water provides, swim en masse to the eastern side of the ocean. "The coastal waters of the East Pacific mostly fall within various countries' exclusive economic zones. If Taiwanese fishing vessel operators can get a timely handle on the shifts in ocean currents caused by warming, they can more quickly sign fishing agreements with the host countries. This improves the competitiveness of Taiwan's deep-sea fishing fleet," explains Lu Hsueh-jung tirelessly.

Insect crisis

Fish in the sea react directly and intensely to changes in water temperature. But it is insects that are regarded as the creatures able to adapt most rapidly to climate change, because their short reproductive cycles enable them to evolve faster.

Scientists expect some organisms to benefit from the climate change while others lose out. "In particular, heat-tolerant species will gradually expand their range, and the survival of cold-zone species will be threatened. For instance, tropical insects may spread all over the world, creating an imbalance of distribution," says Wu Wen-lung, a research fellow at Academia Sinica's Institute of Zoology.

An increasingly hot and humid living environment exposes farmers to the growing threat of insect pests, such as locusts. But the same conditions also favor tropical organisms that can transmit diseases to humans themselves, and the territories affected by them are expanding rapidly.

"For a decade or two now, researchers in other countries have been taking notice of the boost that global warming can give to disease vectors," says Professor Wang Chiu-sen of the graduate institute of public health at National Taiwan University. The list of diseases that may be helped to spread by climate warming includes viral diseases like dengue fever, yellow fever and Japanese encephalitis, bacterial diseases such as Lyme disease and Rocky Mountain spotted fever, and parasitic diseases like filariasis and schistosomiasis.

The expanding range of malaria-transmitting mosquitoes is seen internationally as the first major effect of global warming on disease vectors. According to international research, in the second half of the 21st century the areas affected by mosquitoes capable of transmitting malaria will be at least 30% larger than at present, and temperate zones will not be spared. For instance, with the large volume of air traffic between large European cities and Africa, in recent years malaria mosquitoes (Anopheles gambiae) have caused many malaria cases around European airports. As global warming leads to longer summers in Europe, public health officials worry that in future the African mosquitoes will be able to breed there and colonize the continent.

Dengue moves north

In Taiwan, dengue fever crossed the Tropic of Cancer in 1995, causing academics and medical practitioners to start taking notice of the relationship between climate warming and disease vectors. In the past, dengue fever cases in Taiwan were mainly concentrated in Kaohsiung and Pingtung Counties, and the main vector was the yellow fever mosquito (Aedes aegypti). But despite increased budget allocations for sanitation and healthcare, dengue fever has not been defeated. In particular the Asian tiger mosquito (Aedes albopictus), previously not considered a vector, has now become one, and has caused numerous cases of the disease in Taichung and Taipei. In southern Taiwan, dengue fever cases used only to occur in August and September, but now they continue into December or even January.

To analyze the incidence of dengue fever, Wang Cheng-hsiung, deputy director of the National Institute of Environmental Analysis, examined temperature records for the last half-century. He found that 50 years ago the average winter temperature in Taiwan was below 10°C, but today the island basks in balmy winter sunshine, with temperatures averaging 20°C. In January 2002, the daytime average in Taipei exceeded 18°C on as many as ten days. According to overseas research, says Wang, "at temperatures below 17°C, Aedes mosquitoes become much less active and lose the ability to bite and suck blood; and at temperatures below 18°C, even if humans are bitten by infected mosquitoes, they will not develop the disease." Comparing present and past temperatures, dengue fever's northward advance should come as no surprise.

"The biggest public health challenge of the 21st century is the return of infectious diseases that had formerly been brought under control, and the displacement and expansion of infectious diseases due to climate change," says public health researcher Wang Chiu-sen. He also warns that we should not overlook the risk of respiratory disease caused by pollen being exacerbated as plants' flowering periods grow longer due to warming, and he notes that along the coasts of Central and South America, a type of alga that harbors the cholera bacterium has been spreading widely following the rise in sea temperatures. Occurrence of cholera has jumped to unprecedented levels, to the alarm of disease control experts.

Apart from the threat from disease vectors, a growing body of data shows that many small wild creatures such as snails, frogs and butterflies have become indicators of global warming.

Butterflies and snails

Over the past two years, researchers from NTU's entomology department have been surveying the ecology of butterflies in Taiwan, in the hope of identifying the best locations for butterfly conservation zones. They were surprised to discover that many tropical butterflies have moved north to take up residence in Taiwan. Observations by postgraduate student Li Hui-yung have confirmed that six Southeast-Asian butterfly species have successfully bred in Taiwan. One of them, the golden birdwing (Troides aeacus), has also set a record by flying to Japan, into the territory of temperate- and cold-zone butterflies.

Southeast-Asian butterflies fluttering over Formosa "could very well be linked with global warming," surmises Li Hui-yung, who speculates that if the worst comes the worst, "tropical butterflies may gradually squeeze out the native butterflies of higher latitudes such as northern Taiwan and Japan."

Wu Wen-lung, a research fellow at Academia Sinica's Institute of Zoology, has noticed large shifts in the distribution of Taiwan's mollusk species too. "Pancala batanica pancala, a land snail with a left-spiraling shell, was formerly only found on the Hengchun Peninsula and in Taitung County. But in 1989 it unexpectedly turned up at Shihtan in Miaoli County." Wu cites a land snail called Leptopoma taivanum, the green mussel (Perna viridis) and a chiton named Acanthopleura spinosa as further specific examples of tropical mollusks whose distribution has advanced northward.

Mass extinction?

According to a report issued in February last year by the international Global Coral Reef Monitoring Network, the greatest threat to coral reef survival is global warming. Coral reefs cover only 0.2% of the area of the oceans, yet they provide habitats for a quarter of marine organisms. As seawater temperatures rise, corals worldwide are gradually bleaching and dying. "The situation is worst in the waters off countries around the Indian Ocean, Southeast Asia and the West Pacific, such as Taiwan, the Philippines, the Maldives, Kenya, and the Seychelles," the report states.

The changes in Taiwan's ecology are just the tip of the iceberg of global ecological change. Around the turn of the century, many news reports focused on how the melting of glaciers in both arctic and antarctic regions is causing the habitats of cold-zone species such as penguins, sea lions and seals to shrink rapidly.

Researchers believe that many of the incidents of ecological change that have been popularly attributed to the weather can actually be viewed as one-off aberrations that will not cause long-term genetic change. But looking back at the history of our planet, several warming events have caused mass extinctions. Today, warming caused by human activities is putting the world's species to a stiff test. Can humankind, charged with the difficult task of "managing" the planet, bring them back from the brink? What should our response be? This may well be a stiff test for the human race's own sustainable survival.

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The spirit of spring has reported for duty early. Before the Chinese New Year, cherry trees were blooming all over the mountains of Wulai, attracting many flower lovers to enjoy the scene. (photo by Jimmy Lin)

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Mullet catches have been falling year by year. Apart from overfishing, El Nino events have played a part by affecting the southward movement of cold water from the east coast of mainland China. (photo by Vincent Chang)

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The northward advance of dengue fever across the Tropic of Cancer is an indicator of climate warming. Researchers have confirmed that increased activity of the disease's main vector, the yellow fever mosquito, is related to the rise in winter temperatures in Taiwan. (photo by Hsueh Chi-kuang)

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The arrival in Taiwan of many tropical butterflies from Southeast Asia may also be linked with global warming. Researchers fear their impact on the ecology of native butterflies. Our picture was taken in Yellow Butterfly Valley at Meinung, Kaohsiung County. (photo by Vincent Chang)

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Corals are the most immediate victims of rising sea temperatures. Reports of coral bleaching have come from around the world. (courtesy of the National Museum of Marine Biology)