25 April, 2019


Adaptation – Part IV

By Ranil Senanayake

Dr Ranil Senanayake

Dr Ranil Senanayake

Preparing for the future by looking back.
Understanding the issues and options before us.

There is a need to reforest our mountains to ensure a robust watershed. This seems evident. However, when embarking on such action the questions that arise are: What kind of tree cover are we attempting to establish? What soils will be restored? What landscapes are we looking to create? As discussed before, all traditional development was on a watershed basis. The slowing of the downstream flow through a cascade of tanks is a prime example. Modern development too should pay attention to maintaining the integrity of watersheds.

Development planned on a watershed basis can lead to sustainable settlement. Now that it is evident that access to clean water is going to be a critical need, the retention of rainwater with the least amount of contamination should become an ideal. The most important source of clean freshwater is the aquifers. The aquifers are maintained by recharge by infiltration of rainwater. As an example if an area with 3 inches of rainfall is considered, .6 inches will leave the area as runoff, the rest percolates downward to replenish the aquifer (fig 1). As the amount of impervious surface increases through urban development, the contribution to the shallow aquifer drops to .5 inches. Thus planning for haphazard urban growth, without considering the landscape that it is in, can lead to a loss of water in the aquifer.

Carbon footprint of urbanization must also be computed as the carbon cost to the nation when reporting on our emissions. When every ton of concrete emits 800 kgs of CO2 and every ton of steel is responsible for 1.2 tons of CO2, just the construction of this infrastructure will be carbon expensive. When the ongoing need of energy for its maintenance is considered, urbanization should be approached rationally and not merely pushed by the greed of ‘developers’.rainwater-infiltration-rates-as-determined-by-different-classes-of-land-use

Fig 1. Rainwater infiltration rates as determined by different classes of land use

The following steps to urban development were proposed to the Megapolis Ministry, it is to be seen if rationality is expressed.

  • Each urban center located and identified within a watershed.
  • Each center will recognize the economic value of the ecosystem services supplied by their particular watershed
  • The maximal sustainable yield of ecosystem services of each watershed will be the defining parameters of growth for each center
  • Each center will strive to develop the primary production of that watershed to its highest value.

If such thinking is applied to the current national commitment to Sustainable Development Goals (SDG’s), rational landscapes that recognize watershed boundaries will result (fig 2.) Here each urban center is located and identified within a watershed.developing-a-sustainable-landscape

Fig 2. Developing a sustainable landscape

As people living in urban centers look towards enjoying a healthy life, they can ensure such an outcome by investing in the rural sector to increase the ecosystem services that underlie a good quality of life. What are these services? The provision of clean air, the provision of clean water and the provision of clean food. The provision of clean air is made possible by the production of Oxygen, the removal of airborne particulate matter. The photosynthetic matter or the leaves of plants produce life-giving Oxygen as long as the sun shines. The leaves of plants give out a constant stream of moisture that settles dust and airborne pollutants. The provision of clean water is assured by two mechanisms one is the cleaning and release of water into the air through the evapotranspiration from leaves, the other is by the cleaning action of the soil ecosystems maintained by the roots of the forest. The leaves of plants also, sequester Carbon, make clouds, cool the ambient temperature and provide food. It is in the rural part of a watershed that a large volume of leaves can be maintained. The larger the volume of this green component, the chlorophyll the more ecosystem services that land produces.

In considering the current value of the Carbon trade, estimated by Thomson Reuters Point Carbon, shows a value to €48.4 billion ($52.8 billion) in 2015.

Thus if we consider the value of 52.8 billion dollars to contain climate change, the value of photosynthetic biomass can now be addressed. Assuming that the market would bear at least the value of controlling climate change, on the ability to breathe and drink fresh water, the 93.1 billion tons of photosynthetic carbon currently in stock would be roughly worth about .56 dollar cents 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 before the sequestered carbon is measured. What is valued is the product of the leaves (wood), that acts as a sequestered store of carbon. What should be valued in addition is the Oxygen, clean air, water, cooling that is essential to a healthy life. The interesting fact of placing a value on leaves (photosynthetic biomass) is that they only have value as long as they are living. Thus the rural component of a watershed, could maintain forests not only to ensure retention of rainwater but also to provide health and well being to al those who live within it.

But what forests do we have at them moment? According to the FAO, 28.8% or about 1,860,000 ha of Sri Lanka is covered by trees. Of this, only 9.0% (167,000) is classified as primary forest, the most biodiverse and carbon dense form of forest. This should be a shameful statistic for a country that sells itself as a ‘biodiversity hotspot’. The rest is degraded forest, plantations and home gardens. With 185,000 ha of planted monoculture tree plantations, the country has more plantations than primary forest.

But only 9% primary forest? Should this not be a cause for national alarm? We claim to be a ‘biodiversity hotspot’ and we have only 9% our primary forests to protect this biodiversity. The tragic reality of this much vaunted boasting about our biodiversity ‘hot spot’ claims, is that many of the endemic species are found in the small forest patches, which represent the only remaining habitat for many rare, indigenous or endangered species. These patches are the small bits of forest that remain on steep or inaccessible parts of the rural landscape. These forest patches have, in most cases escaped the axe and plow due to the fact that they were difficult to access, but with an increase in land hunger and political corruption, they too are being targeted for destruction. As these ecosystems exist as small patches (0.5 – 10 ha) of refugial vegtation, they are the most endangered and receive least attention.

The current rush to capitalize our forest stocks by getting money for their carbon storage capacity only, is shortchanging ourselves. There are initiatves like the REDD of the UN which recognizes the very valuable function of an existing forest as a ‘store’ or bank of sequestered carbon and pays for the time that it will store or hold its carbon from entering the atmosphere through deforestation. But this misses the fact that such forests also provide a massive amount of ‘ecosystem services’ such as Oxygen generation, water cleansing , ambient cooling, cloud production etc. that is not paid for, just paying for sequestered carbon only, is paying only for one service and getting the rest for free. Carbon trade must accept the value of the other ecosystem services if we are to move towards an honest economy. Such a move, the recognition of the value of the ecosystem srvices provided by living leaves (photosynthetic biomass), can create the economic drive to restore our landscapes and benefit from the vast construction of reservoirs bequeathed to us by the past.

To be continued….

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