Rainforests: Where Trees Celebrate Life

clouds above rainforest

Clouds form above rainforests from moisture released by leaves

Rainforests, and especially tropical rainforests, is where life thrives with all its originality and creativity. These conditions are wet and for tropical regions, warm. This luxurious climate is perfect for growth, but there is also fierce competition for light and nutrients. It is humid beneath the canopy but pleasantly cool above where water is released through leaves to form clouds. Thus these forests have a dramatic effect on Earth’s moisture and heat circulation while providing 28 % of the planet’s oxygen.

Rainforests have been around for tens of millions of years and have adapted with continental drift and glaciation e.g. the Daintree rainforest in Queensland, Australia, is thought to be 135 million years old and contains about 30 % of all reptile species on the continent. It is thought that not only the excellent growth conditions, but also time, allowed for increased diversity, complexity and symbiotic relationships to form beneath the dark canopy.

Rainforest

Abundant life is beneath the rainforest canopy

This biodiversity in rainforests provides 25 % of all Western pharmaceutical ingredients, yet only 1 % of tree and plant species have been examined. One hectare of rainforest contains approximately 750 tree species and 1500 plant species. A quarter of all insect species are also thought to exist in these forests. We should also be most grateful for tropical forests providing 80 % of our diet…including avocados, coconuts, figs, oranges, lemons, grapefruit, bananas, guavas, pineapples, mangos and tomatoes; vegetables including corn, potatoes, rice, winter squash and yams; spices like black pepper, cayenne, chocolate, cinnamon, cloves, ginger, sugar cane, tumeric, coffee, vanilla and nuts1.

chocolate

Chocolate comes from cacao plant seeds, native to South American rainforests

Yet we are painfully slow to see their real value. Modern humans have only seen timber, pasture land for cattle and what potentially lies beneath the soil in the form of oil and gas. We destroy most of the real bounty and wealth to create a beefburger. Even indigenous humans who live in rainforests have suffered from this modern greed; 500 years ago there were 10 million Indians living in Amazonia, this has been reduced to less than 200 000 today. Though it is hard to call it greed when most of the value of rainforests is not used for human benefit; ignorance is a better word, yet this also fails to fully encompass repetitive and willful destruction.

The beefburger

Rainforests are often cleared for pasture...to finally make a beefburger

Decisions are required by all of us. As a human the Earth forms part of our identity and so, even if implicit, the destruction of a vital organ of the Earth is an act affecting all, and requires a response. The trees around us should remind us of this; as their kin are ‘cleansed’ we should reflect on our way of life. For myself, this introversion realises itself in a project to help the Earth, and thereby hopefully ourselves.

deforestation

Clearing of the rainforests (Greenpeace)

  1. http://www.rain-tree.com/facts.htm

The Natural Powerhouse

While humans have proudly developed their own power sources using mostly fossil fuels, uranium and rivers, photosynthesis in nature captures approximately 6 times as much energy consumed by modern civilisation. This capture rate is about 100 terawatts, gained from our closest star, the Sun.

The Sun

Trees love the Sun (Soho Extreme Ultraviolet Imaging Telescope, EIT Consortium)

How is this done? The leaves of trees and plants have tiny organelles containing chlorophyll which absorb mostly blue and red light, so we see them as green. An idea of this global activity can be observed in the world map showing concentration of chlorophyll in the sea (from phytoplankton), and vegetation concentration on land.

Chlorophyll Map

Chlorophyll Map of Earth. Sea shows chlorophyll concentration and land shows relative vegetation index.

This energy captured promotes, through the production of electrons, the reaction between carbon dioxide from the atmosphere and water to produce sugar and oxygen. In trees, the water comes from the roots transported via the xylem (see previous blog) and reacts with carbon dioxide which enters through tiny holes in the leaf, or stomata (see pic).

Tomato leaf Stoma

Leaf Stoma

The sugars produced are then transported via the phloem to the roots. The basic reaction is 6CO2 + 6H2O –> C6H12O6 (sugar) + 6O2, meaning for each part of carbon dioxide reacting, an equivalent amount of oxygen is produced.

In this way a mature tree can provide enough oxygen for 2 people to live per year, while in total, photosynthetic organisms convert about 100-115 petagrams (15 zero’s!) of carbon into biomass per year.

The competition for light in the forest is intense and sometimes trees are growing too close to each other, thereby undermining each other’s health. Shade tolerance is therefore a key competitive advantage. However, with human activity, competition for light is the least of a tree’s worries. Trees have evolved at different latitudes in different ways to capture this light. At the equator where the sun is overhead all year round, trees have broad canopies. While at higher latitudes trees generally have narrow and extended crowns to capture light at lower angles, e.g. conifers.

There is thus perhaps a simple way of being more conscious of trees and having them in our awareness, if on a sunny day we can occasionally be mindful when we enjoy a deep, luxurious breath of air, and think about that oxygen that sustains us.