Forests lock up carbon

Sections

Mabira Forest

Semuliki Forest

Big, Old Trees

Trees improve air quality

Tree arithmetic

Most countries have realised that it has been a mistake to cut down their forests and that the amount of CO2 in the atmosphere by planting many more trees. Uganda has lost much of its forest in recent years, but some impressive forests still remain and strong efforts are being made to preserve them.

Mabira Forest

The whole of the land from Kampala to Jinja, in Central Region, was dense equatorial forest as recently as the 1970s. In the years since, forest has been cleared for farming, industrial sites and to extend the sugar and tea plantations around Lugazi. Mabira Forest is what remains of a huge forested area. Mabira Forest is the the east of Lugazi on the Jinja Road. While many of the very big trees have been illegally felled, the forest that remains is impressive. It over 300 sq. km. and a large part of it is a nature reserve. The forest has 312 species of trees, 315 species of birds, 218 Butterfly species and is home to 23 species of mammals, including primates.

The trees in Mabira locked up 8.5 million tonnes Carbon in 2018 and each year the forest absorbs an additional 150,000 tonnes of Carbon per year. So it is a very important carbon sink, which releases huge quantities of oxygen into the atmosphere.

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Semuliki Forest

Semuliki is another very important forest, which forms one of the important “lungs” of Uganda – absorbing huge amounts of carbon and emitting live-giving oxygen. The Forest is in Bwamba County in Bundibugyo District. It straddles the Semuliki River, which forms the boundary between Uganda and the Congo. Semuliki became a National Park in October, 1993, so it is one of the newest parks in Uganda.

It covers an area of 220 sq km and is one of the richest areas of flora and fauna diversity in Africa, as it is the meeting point of several climatic and ecological zones, including being part of the Congo basin. The dominant tree species is Uganda ironwood, which can grow up to 46 meters and the larger trees have hollow boles and buttress roots (see picture above). As well as a varied flora, Semuliki has a rich diversity of fauna. There are over 400 bird species and 60 mammals including buffalo, elephant, leopard, hippopotamus, 8 primate species, bush babies, flying squirrels and 460 species of butterfly.

As well as acting as important carbon sinks, the biodiversity of Mabira and Semuliki Forests make them important sites of scientific interest across the world. Both forests attract many tourists, whose spending provides jobs and income. There is huge potential to expand the income from tourism so long as the forest habitat is conserved.

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Big, Old Trees

Research by William Morris at the University of Melbourne, Australia has shown that big, old trees are important:

  • Large, older trees add more growth in new branches and leaves and absorb carbon dioxide more rapidly than younger, smaller trees.
  • Research published in the journal Nature shows that in 97% of tropical and temperate tree species, growth rate increases with size. This suggests that older trees play a vital role in absorbing carbon dioxide from the atmosphere.

David Lindenmayer, a professor of environment at the Australian National University, described findings of the study as being of global significance. “It highlights why it is really important that we grow as many areas of forest through to being old growth forests as possible,” he said.

The more carbon we can store in forests, the more chance we have of reducing the effects that are going to arise from massive climate change. Storing large amounts of carbon in forests is absolutely critical and the way you do that is to have big, old trees.

Lindenmayer said that the study highlights flaws in current forest management policy, where big, old trees are often cleared first to provide pulp and timber. “The value of native forests for carbon storage and for maintaining biodiversity, significantly outweighs their value for pulp and timber.” he said.

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Trees Improve Air Quality

Reference: http://urbanforestrynetwork.org/benefits/air quality.htm

It is now widely recognised that healthy forests are essential for improving our air quality.

On average, one acre of new forest can sequester about 2.5 tons of carbon annually. Young trees absorb CO2 at a rate of 13 pounds per tree each year. Trees reach their most productive stage of carbon storage at about 10 years at which point they are estimated to absorb 22 kg of CO2 per year. They release enough oxygen back into the atmosphere to support two human beings. Planting 100 million trees could reduce an estimated 18 million tonnes of carbon per year.

The combination of CO2 removal from the atmosphere and carbon storage in wood makes trees extremely efficient tools in fighting the greenhouse effect. Planting trees remains one of the most cost-effective means of drawing excess CO2 from the atmosphere. If every family planted one tree, the amount of CO2 in the atmosphere would be reduced by 10 million tonnes annually.

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Tree Arithmetic

  • Annual global CO2 emissions are 36 billion tonnes.
  • World population is 7.6 billion.
  • Average emissions of CO2 are 4.7 tonnes per person.
  • Removal of 1 tonne of CO2 from the atmosphere requires 15 trees.
  • So, we need 71 mature trees per person to balance the emissions.
  • To cover the emissions of the whole world population the Earth needs to have 450 billion mature trees.
  • The most recent estimate of the number of mature trees in the world is 400 billion.
  • So, we need an extra 50 billion trees to be planted and cared for to maturity.

This implies that if every person in the world planted 7 trees and cared for them to maturity, we could eliminate the surplus carbon in the atmosphere. This is quite an ambitious target. However, if we take the other carbon reducing measures described above and governments also organise large-scale tree planting, then even small amounts of tree planting by individuals can make a big difference..

Reference: UN Food and Agriculture Study of the Uses of Forest Resources in Africa:
http://www.fao.org/3/t9450e/t9450e03.htm#TopOfPage

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