Shades of Green: Earth's Forests -- Seasons

Throughout most tropical forests, some rain falls at all times of the year. There is often a definite dry season which usually lasts three to four months, although in extreme conditions it can last anywhere between two months and as many as ten. The severity of the dry season depends on location. In some places, the tropical trees lose their leaves during extended droughts, and grow new ones when the rains begin. Since tropical forests extend for great distances in some areas, one part of the forest may be experiencing its dry season while the rainy season progresses in a different area of the same forest. When the wet season begins on one side of the equator, the dry season usually begins on the other.

Tropical wet and dry seasons bring significant changes for the forest animals and plants. Since the rainy season brings dense clouds, plant structural growth is often greater at other times of the year when there is more sunlight. Trees also flower more often in the dry season when pollinating insects aren't stopped by heavy rains. Seeds that sprout at the beginning of the rainy season have a better chance of survival because there will be an adequate water supply for their first critical months.

The coral tree (Erythrina saundwicensis) is widespread in the tropics. It is deciduous, and flowers during the season when it has no leaves. Photo courtesy Al Walters.

Insects are far more abundant during the wet season. This is also the time when most trees are growing the largest numbers of fresh leaves, so there is plenty of food around for these insects. Similarly, most birds nest at the beginning of the wet season, so there will be the most insects available just after the eggs hatch.

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