This article is part of a three-part series on Oceans and Coral Reefs consisting of the following articles:

  1. Rainforests and Coral Reefs
  2. Ocean Prognosis
  3. Coral Reef Solutions

Each has been taken from the Mongabay main site and adapted to meet 5th grade educational standards. Ideally, they are to be read in the above order.

Rainforests and Coral Reefs

The Makers and Movers of Rain

Groundbreaking research shows that rainforests and coral reefs create rainfall.

Coral reefs and rainforests seem to have little in common. One is found in the ocean. The other is found on land. But, they are both hotspots of biodiversity and they both may seed clouds and produce rainfall.

Reefs and rainforests in New Guinea. 

Do you remember learning about the Water Cycle?

picture credit:

Simply put, water evaporates from the oceans or lakes and rises into the air as vapor or steam. Once in the sky it condenses or turns back into water and forms clouds. Last it precipitates or rains down on the earth once again. The cycle repeats over and over. The water we drink is as old as the earth.

It is actually much more complicated than that. Scientist Markus Petters from North Carolina State University explains, “Trees basically ‘sweat out’ organic molecules that react with compounds in the atmosphere, producing tiny particles that are around 20 to 200 nanometers in size,” (that is too small to see with your naked eye). “These particles seed the clouds.” So without these very small

nano-particles, clouds will not form.

Rain over the rainforest. Photo credit: Rhett Butler

It turns out that in the air above a rainforest 80% of the particles in a raincloud come from organic forest material.

But, it’s not just tropical forests that have the power to produce rain. Dr. Graham Jones of Australia’s Southern Cross University believes that a thriving coral reef also seeds clouds and brings precipitation. Coral reefs produce a substance called DMS or dimethylsulphide, which enters the atmosphere when water evaporates. These are tiny particles around which water vapor condenses to form clouds Jones explained to, adding that, “water vapor cannot form clouds without these tiny particles being present.”

“Consequently,” Jones says, “no clouds, no rain in the regional areas where reefs occur.”

Beginning rain clouds over a coral reef. Photo credit: Pacific Promotion Tahiti

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The DMS is made by the algae living in coral, causing the corals to produce the cloud-seeding substance on a daily basis. Jones says that his research shows that the coral reef-produced rain may actually feed rainforests along Australia’s northern coast.

However amazing these studies sound, the boldest theory linking ecosystems and precipitation was produced by two Russian scientists who say forests act as natural pumps to move rainfall from coastlines to the interior of continents. It was thought that winds caused by earth’s rotation moved the clouds. Now it may be that the vertical movement of water vapor around forests is also responsible.

While scientists are still trying to understand how forests and reefs are responsible for precipitation and rainfall patterns, there is no question that these ecosystems are endangered.

The Amazon rainforest faces threats from commercial farming, cattle ranching, logging, oil and gas, dams, road construction, and slash-and-burn farming.

Coral reefs are no better off. Pollution, ocean acidification, overfishing, and climate change may cause many coral reefs to vanish before the end of the century. In addition, Jones has found in his studies on reefs that even a slight rise in ocean temperatures could affect the coral’s ability to produce the small DMS particles, making climate change a bigger threat to clouds and rain produced by coral reefs.

A clown fish in Indonesia. Photo credit: Rhett Butler

If these theories withstand the test of time, and science, they could change the way we think about both forests and coral reefs: the ‘makers’ and ‘movers’ of rain.

Adapted from the following articles:

Jeremy Hance on 15 October 2010 and 3 March 2010