365 Days of Climate Awareness 66 - Tropical Rainforest

Rainforests, both tropical and temperate, are forest ecosystems featuring a canopy which blocks most direct sunlight, an understory of tree trunks and branches, and the plants which grow on them, and a sparsely vegetated floor due to the low light, and enough moisture to prevent forest fires. The world's best known is the Amazon, which comprises roughly 50% of all tropical rainforest worldwide.

Schematic of a rainforest.

Tropical rainforests typically have no dry season and are within ten degrees' latitude of the equator. Temperate rainforests occur outside of the tropics (more than 23.5° N/S), and experience typical seasonal temperature changes. It is estimated that rainforests house 40-75% of all species, and are responsible for 28% of global oxygen production (though much of this is consumed again so the net to the rest of the world is not large).

Zones of temperate rainforest.

The canopy is poorly understood compared to the understory and floor, due to its inaccessibility. Most non-insect animals live in the understory, on the trees. Insects occupy the understory and floor, where fungi are also found. The topmost layer of soil is rich and organic, but a few inches below is laterite--clay washed out of almost all nutrients, due to the constant drainage of water. A feature which increases the biodiversity of the rainforest are the refuges--how the forest itself and topography provide shelter for many species, including plants, from predators.

Zones of tropical rainforest.

One of the most important aspects of the rainforest biome is evapotranspiration, the role the forest plays in the water cycle. Rain falls on the forest. Some evaporates but most eventually makes its way to the ground, where much of that is taken up again by plants. During photosynthesis and respiration, the plants expel water vapor to the atmosphere, effectively recycling the water. This happens on a large enough scale to be of significant impact on regional and global climate.

Deforestation of the Amazon.

The Amazon rainforest, some 7M km² (2.7M mi²) in extent, is being rapidly cut back by commercial development for farming and industry. As of 2018, an estimated 17% of the forest's pre-industrial extent had been lost to human development. It is hypothesized that the destruction of 25% of the forest will result in the region's biome changing characteristics from rainforest to savannah. Over the past two years the pace of Amazon deforestation has increased.

Tomorrow: evapotranspiration.

Be well!