Project BudBurst Why is Phenology Important?

Though we don’t usually talk about the seasons and plant growth in terms of phenology, it has an enormous impact on the natural environment and how we interact with it in our everyday lives. Because plants are at the base of the food chain, anything that affects plants ripples out to affect the rest of the ecosystem.

Phenology is important because…
…it affects whether plants and animals thrive, or survive, in their environment
…our food supply depends on the timing of phenological events
…changes in the timing of phenological events can be used as an indicator of climate change

Phenology affects whether plants and animals thrive, or survive, in their environment.
The success of an ecosystem or food chain depends on the timing of phenological events. Many animals rely on leaves, buds, flowers and fruit for their food. If the timing of the emergence of leafs, buds, and flowers is greatly changed, it can result in fewer seeds and insects which would impact the animals that depend on insects for their food.

Consider a mouse for example – some mice eat insects and seeds. If plants bloom early, they may be finished blooming by the time their pollinators (insects like bees or butterflies) are mature enough to pollinate their flowers. This reduces two of the mouse’s food sources – if the flowers aren’t pollinated, there are no seeds, and if the insects don’t have food, there are no insects. If there is less food, fewer mice survive, so predators like snakes and hawks, which depend on mice as a food source, will also go hungry. (Figure modified from A Terrestrial Food Chain, copyright Addison Viesley Longman, Inc)

From the historical records and observations, we know that phenological events can vary from year to year. Ecosystems can recover from variation between years, but when these changes happen consistently over many years, the timing of events such as flowering, leafing, migration, and insect emergence can impact how plants and animals are able to thrive in their environments.

Phenological events affect our food supply
Changes in phenological events can also have a significant impact on how we live our lives and interact with our environment on a daily basis. For example, when plants flower and fruit can affect our health and food supply.

For many plants, the growing season is triggered by rising air temperatures. Fruit trees for example flower in response to rising temperatures. Take cherries for example. Cherry trees flower in response to warming temperatures, so if it is warmer earlier in the year, the flowers will bloom earlier as well. There is evidence that this is actually happening some places in the country. For example, Washington DC has traditionally had a Cherry Blossom Festival during the first two weeks in April, culminating in mid April with a parade. Over the past few decades, the cherry trees have been blooming earlier and earlier, so that peak bloom is now at the beginning, rather than during the celebration at the end of the festival.

Cherry trees, as well as many other fruit trees like apples, peaches and pears, are pollinated by insects, which have a seasonal life cycle – they take time to develop from egg to larva to adult. If the trees flower earlier in the season, they may be out of synch with their pollinators. For example if an insect is still in the egg or larval stage, they will not be able to fly from tree to tree and transport pollen from one plant to another. Without pollination, the flowers are not fertilized, and will not produce fruit.

In addition to affecting our food supply, phenological events can also affect human health. Pollen allergies can be exacerbated by some changes in growing conditions. People are allergic to pollen from all kinds of plants, and when the flowering time changes, those reactions will change as well.

Phenological events can be used as an indicator of climate change
Scientists can use changes in the timing of phenological events to determine how the climate changes over time. Scientists use phenological data in computer models that project future climate scenarios and the projected impacts of such changes on the environment. It is important for us to know how the climate is changing because the impacts of climate change are far-reaching.

Species Distribution - 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.
Spread of disease - The spread of diseases carried by insects and other animals such as malaria, viral encephalitis, Chagas disease and African sleeping sickness is also a concern. These diseases are transmitted by what are called “biological vectors” – animals that carry a disease pathogen within their body. They are usually, though not exclusively, arthropods, such as mosquitoes, ticks, fleas and lice and transmitted by a bite. As climates warm, the animals that carry these diseases expand their range, surviving in areas that in the past have been too cold for them to survive. Recently instances of malaria have been reported in both Texas and in Florida.
Extreme Weather - Heavier rainfall causes flooding in many regions as warmer temperatures speed up the water cycle. In the last ten years, floods have caused more damage than in the previous 30 years. Some researchers say that the number and strength of hurricanes, tornadoes, and other events has increased over the last 15–20 years. However, scientists are still looking into this.
Changing Ecosystems - As temperatures warm, species may migrate to cooler places or die. Species that are in particularly danger include endangered species, coral reefs, and polar animals such as penguins, polar bears and seals. There have been changes in where we can farm: As climates warm, some mid-latitude places, like Europe, are getting a longer growing season, while some tropical places are becoming too hot and dry to grow crops.