The studies, published in 'Science' magazine, add to the growing body of research providing anecdotal evidence that regional changes in climate, particularly increases in temperature, are causing glaciers to shrink, permafrost to thaw, and wildlife behavior to change.

''You are never 100 percent sure but what seems clear is that these changes fit very well with a general trend of warming linked with human activities,'' Josep Penuelas, a scientist at the Autonomous University in Barcelona who authored one of the studies, told IPS.

The findings were released just before international climate treaty negotiators are scheduled to meet in Morocco Oct. 29 - Nov. 9.

''An increasing number of studies now report changes in plant and animal cycles from a wide range of regions, from cold and wet to warm and dry ecosystems,'' Penuelas said in his peer-reviewed article, 'Response to a Warming World.'

In the Mediterranean, the leaves of most deciduous plant species now unfold on average 16 days earlier and fall on average 13 days later than they did 50 years ago. From Scandinavia to Macedonia, researchers have observed a six-day shift to earlier leaf unfolding and a five-day delay in autumn leaf coloring over the past 30 years.

Remote sensing satellite data further validate these ground observations, said the study. New data suggests that the growing season has become nearly 18 days longer during the past two decades in Eurasia and 12 days longer in North America.

All the observed plant changes ''are highly correlated with temperature changes,'' Penuelas said.

Insect, amphibian, and bird life cycle changes, according to the study, were also observed. Butterflies now appear 11 days earlier than in 1952 in northeast Spain.

Frog calling, which starts when the weather gets warmer, has been reported to occur about 10 days earlier between 1990 and 1999 than between 1900 and 1912 in New York State. Surveys in Britain showed birds laid their eggs nine days earlier in 1995 than in 1971.

These changes in animal and plant cycles could prove to be harmful, said the study, because migratory species could wrongly decide when to start spring migration. Species that migrate from tropical wintering grounds, such as south of the Sahel, to temperate breeding grounds, may arrive at inappropriate times and unsuccessfully compete with other wildlife.

''Climate change may thus be a serious threat to species,'' it said.

The second study provides a unique set of ''nontraditional'' data based on an 84-year betting contest held on a frozen Alaskan river. Known as the Nenana Ice Classic, people in the small remote town of Nenana, Alaska have been betting money every year since 1917 on when a wooden tripod erected on the frozen Tenana River will fall through the thawing ice.

Researchers at Stanford University compared the Ice Classic contest records with available climate data for the area and found that ice breakup occurs on average five days earlier than it did in 1917.

Raphael Sagarin, one of the researchers who co-authored the study, told IPS that the article underscores the importance of amateur naturalists, hobbyists and indigenous peoples who have collected observational data on nature over long periods of time.

From these records, he said, scientists now have many examples that show that the natural world has been responding to climate warming.

''Amateur naturalists have been so important in our ability to understand how climate change has affected natural systems because scientists for the most part weren't keeping these data,'' said Sagarin.

Most scientists believe that carbon dioxide and other heat- trapping greenhouse gases, emitted when oil, gas and coal are burned, are causing the gradual rise of Earth's air surface temperature.

In January, an international group of scientists known as the Intergovernmental Panel on Climate Change (IPCC) predicted that the average surface air temperature of the planet would rise by 1.4-5.8 degrees Celsius by the year 2100 relative to 1990. Average sea level worldwide is projected to rise by 0.09-0.88 meters by 2100.

The panel, in conclusions supported by the studies released Thursday, said many species of mammals, invertebrates, reptiles, birds, amphibians and insects already are being affected.

Many natural ecosystems - including glaciers, coral reefs, mangroves, and polar regions - are vulnerable to these changes and some will be irreversibly damaged, it said.

Hoping to slow the warming, representatives from hundreds of countries will meet in Marrakech next week to translate into legal text the agreement made in July on the Kyoto Protocol on climate change. This would enable countries to ratify the treaty and turn it into international law.

In July, governments from 178 countries formally adopted a political agreement on the rules for implementing the Kyoto Protocol. The accord, named after the Japanese city where it was drawn up, calls for the 38 industrialized nations to reduce, by 2012, their combined annual greenhouse gas emissions to an average of 5.2 percent below their 1990 levels.

The European Union, Canada, Iceland, New Zealand, and Norway have said they will ratify the agreement while Japan has said it wants to see the agreement come into force by 2002. Australia and the United States - the world's leading emitter of greenhouse gases - said they would not ratify the treaty.

Copyright © 2001 IPS-Inter Press Service

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