Phenology is the study of the timing of life cycle events like leafing, budding, and blooming in plants. The timing of phenological events of many species has changed recently as a result of changing temperatures and rainfall patterns. The average global temperature increased by 0.6°C ( 1.0°F) during the 20th century. The temperature is predicted to rise with another 1.8 to 4.0°C ( 3.2 to 7.2°F) in the 21st century. While this may not appear to be a significant increase in temperature, just small variations at the global scale can have dramatic and varied effects on the environment. For example, scientists believe that this will cause the sea level to rise with 10 to 89 cm (4 to 35 inches) during that time.
Climate change has the largest effect on plants because, unlike many animals, they cannot move easily from one area to another. As a result, the growing season could start earlier or continue over a longer period of time. The timing of phases of the plant life cycle, known as phenophases, are directly affected by temperature, rainfall and day length. Therefore, by monitoring changes in phenological events such as first bud, budburst, and flowering, scientists can detect climate change.
Climate change affects individual plant species by changing the speed and duration of physiological (life) processes such as growth rate, the degree of evaporation of available water, and their interactions with birds and insects. Because plant species differ in their sensitivity to temperature and humidity, climate change also affects the kinds of plants and animals that can survive in an ecosystem. While the number of wild plant species can increase because of climate change, most newcomers are species that perform well in human made environments such as roadsides, agricultural lands and urban areas. Species with more specific habitat requirements, on the contrary, disappear. Although there are many factors that affect species survival, climate change is considered a significant cause of decreased native plant populations.