By Ranil Senanayake –

Ranil Senanayake

Addressing Climate Change: Part III

The third question was on the value of Photosynthetic Biomass (PB). It is basic high school knowledge that the production of Oxygen, sequestering of Carbon, water cycling and ambient cooling is carried out by the photosynthetic component of biomass. It is these very same actions that are being accepted globally as Ecosystem Services with recognized economic values. But the thing that produces these services is being lost at an exponential rate, due to the fact that these Ecosystem Services have not been valued, nor economically recognized.

Although the volume of living biomass as now been captured on most global models of carbon cycling and as the measure of living biomass is being used in the evaluation of carbon stocks with increasing frequency, there is a an urgent need to address the fundamental differences between the components of living biomass. Living biomass is present as two fundamentally different components, photosynthetic biomass and respiring biomass.

Photosynthetic biomass performs the act of primary production, the initial step in the manifestation of life. The biomass so termed has the ability to increase in mass through the absorption of solar radiation while releasing oxygen and water vapor into the atmosphere. As outlined above, it is only photosynthetic biomass that powers carbon sequestration, carbohydrate production, oxygen generation and water transformation, i.e. all actions essential for the sustainability of the life support system of the planet. Yet currently, it is only the product of photosynthetic biomass, as sequestered carbon, usually represented by wood/timber that has been recognized as having commercial value in the carbon market for mitigating climate change. The photosynthetic biomass for terrestrial ecosystems is largely composed of the leaves of terrestrial vegetation, it is the leafy component that contributes to primary production. This component varies greatly in size and temporality.

In computing value, the relative value of leaves have to be considered in terms of their representation in different ecosystems. In a forest, shade-tolerant, late-succession tree species possess significantly larger leaves compared to early-succession, shade-intolerant species. Usually, leaf sizes and leaf numbers tend to be negatively correlated, i.e. the larger the leaf-size the less in number and vice-versa.

The sheer power of operation of the terrestrial photosynthetic system is seen when the volume of water released from photosynthetic biomass is considered, at a water release rate of 100:1, where over 100 molecules of water are released for each molecule of carbon dioxide absorbed by the leaf. The quantity of water released annually by forests and grasslands are like aerial rivers cycling about 6250 billion tons of water into the atmosphere per cycle. This quantity of evaporative water not only greatly influences local cooling events, but also contributes to the distribution of heat in the atmosphere. One of the most significant consequences of evapotranspiration by terrestrial vegetation is the cleaning effect on groundwater, releasing polluted ground water freed of the chemical pollutants that it was once burdened with. This cleaning function is hardly recognized nor evaluated.

The oxygen generation function is taken for granted, but as the recent studies of the hole in the stratospheric shield of ozone show, the phenomenon is expected to last for several decades. Increasing the oxygen producing function of the biosphere, can certainly contribute to the stabilization of the ozone shield. It can also help to allay the impact of massive rates of combustion required for much of modern society. However up to date we have failed to recognize the economic value of the oxygen generation function.

It seems imperative that a real value be placed on photosynthetic biomass; initial computations can begin by considering the current values suggested for the global market for similar functions. The estimated value of the carbon market was in excess of 250 billion. Thus if we consider the current value of 125 billion dollars that has been placed on containing climate change, the value of photosynthetic biomass can now be addressed. Assuming that the market would pay at least the value of controlling climate change, the 93.1 billion tons of photosynthetic carbon currently in stock would be roughly worth about 2.20 dollars per kilogram.

This comes as a surprise when the current models of carbon sequestering to combat climate change is examined, many models discount or place a low value of leaves and twigs which are often removed or bulked before the sequestered (fixed) carbon is measured. This photosynthetic biomass, often considered being too short lived in accounting for carbon sequestering. But it is actually the most valuable component.

Slowing down the loss of global terrestrial photosynthetic biomass stock is not an option – it is a critical need! A massive investment must go towards incrementing the global photosynthetic biomass stock. The potential value of this stock can also attract the investment to develop market growth.

The current approaches to tree farming and forest management needs to accept this potential of photosynthetic biomass and work towards realizing its value. For management purposes, the photosynthetic biomass of a natural ecosystem has to be seen as a continuum of native species from the early seral or developmental stages represented by annuals and short-lived species, to shrubs and bushes, to pioneer trees, to the mature tree dominated, old growth forest. If each stage is encouraged to carry its full complement of photosynthetic biomass, it will help ensure that the management plans address the generation and maintenance of the optimal levels of photosynthetic biomass in each seral stage and gain the corresponding value.

This questions raises the possibility that most nations moving towards a responsible development paradigm could capitalize their standing photosynthetic biomass and find the resources required for their progress away from fossil addiction. As Sri Lanka has stated its goal of moving away from fossil addiction building policy around these climate realities, will assist in building new options for the future.