With fewer forests, we lose 95% of carbon trap

Climate change requires us to ask questions about the environment differently.

It may no longer be enough to ask about forest cover.

How well  forests can sequester carbon dioxide may be the  important question to answer.

What is left of our forests today are  found in middle mountains and high elevations.  These are technically called  mid-mountain and mossy forests.

Forests in the tropics achieve optimal or maximum growth in  the lowlands.

Unfortunately,  our  lowland  forests  are already gone and have given way to agriculture.

Forest trees are tallest and at their largest  in areas within an   elevation  of 0 to 800 meters above sea level.

Trees growing at higher altitudes are smaller in diameter and shorter in height.

Trees in the mossy forest are stunted and their moss-covered branches are gnarled.  Needless to say, the combined volume (or biomass) of mossy and mid mountain forests is far lower compared to a lowland forest.

Giant lauan trees grow in the lowlands. These trees which belong  to the  Dipterocarpaceae family used to dominate  forests   in the lowlands by as much as 80 percent of the entire tree population.

On the average, a mossy forest tree  is 5 meters tall and 40 centimeter in diameter at breast height.   In contrast,   a lauan tree is over 50  meters high and over 100 centimeter in diameter.

Lowland forests have biomass roughly 10 times  larger  than high-altitude forests.

The trunk, branches, twigs, roots and leaves  make up the tree’s biomass, which is basically cellulose  made up of carbon, oxygen and hydrogen  molecules.

As such they store  large amounts of carbon dioxide-  the reason  scientist consider wood  a major repository of carbon sequestered from the atmosphere.

The  larger  the biomass, the bigger amount of carbon a tree  can capture  from the air.

Thus, lowland forests   trap much more carbon  dioxide than mid-mountain and mossy forests.

In 1935, the Philippines  forest cover was estimated at 17 million hectares or roughly 60 percent of our total land area.

Today, only five to seven  million hectares of forest  remain or  less than 20 percent of the land area.

This implies that we have lost 12 million hectares of forest during the last 75 years or about 40 percent of the land has been denuded.

When we compute the Climate Change service of a forest, we refer to the capacity  to sequester  carbon dioxide.

With biomass of lowland forests  10 times more than our remaining mid-mountain and mossy forests today, we  may have lost already 95 percent of  the forest’s capacity to capture carbon dioxide.

This comparison should make us realize that the damage to our forests is more than what we  ever imagined.

The  challenge ahead  is more formidable than it already appears.

We need to grow taller and bigger trees, and not just the midget gmelina and ipil-ipil.

The chances of growing lowland forests dominated by towering lauan trees are not promising though.

Lowlands are generally  already compromised to agriculture, settlements and built-up areas.

But we still have  river banks,  steep slopes at moderate elevations and  ravines.

Collectively these areas could be sizable and their  combined ability to sequester carbon dioxide from the atmosphere could be substantial.

It may not be too late to establish a forest just as tall, just as big, just as grand, and just as large a repository as that needed to trap harmful   greenhouse gases that are part of Climate Change.

(The author is a licensed forester and an expert in forest land use planning. He is a former Regional Executive Director of the Dept. of Environment and Natural Resources in Region 7 and Region 10)