Covered by ancient pines and great mountain scenery, Caledonia Forest has for a long time served as a landmark for Scotland. This forest once covered a large portion of the Scottish highlands, acquiring it name from the romans who referred to Scotland as ‘Caledonia’, implying ‘wooded heights’. The ancient pinewoods that covered the western part of Europe’s boreal Forest are said to have once covered 1.5 million hectares typified by a vast wilderness of birch, scot pine, rowan, juniper aspen, and other trees. The Oak and birch trees covered the west coast ecosystem known for its richness in ferns, lichens and mosses. Unfortunately, the Scottish forests have increasingly faced much damage over the years. Human activities that include lumbering and agriculture contributed significantly in the destruction of these forests. However, over the past years there has been an increase interest on the effect of acid rain on forests. Consequently, this work details the effect of acid rain on the forests in Scotland (Read, and Tanguy, 485-499).
To help appreciate this subject, it is good first to understand what we mean by acidic rain. Rainwater is characteristically acidic owing to the dissolved carbon dioxide that is present in the atmosphere. However, the acidity-handled hare is that which comes from manmade pollutants that get into the atmosphere and dissolve in the rain. This acidity is largely attributed to oxides of Nitrogen and sulphur that find their way into the atmosphere as washouts. Once dissolved in rainwater, these oxides form harmful pollutants after mixing with other chemicals present in the atmosphere. The resulting pollutants either settle on forest trees as ‘dry deposition’ or washed off into the forest soil as ‘wet deposition’. The most common manmade acids in rain are nitric (HNO3) and sulphuric (H2SO4) acid. Other than getting into the forest ecosystem as wet and dry deposition, acidic pollutants can find their way into the forest as water droplets. Here the acid takes the form of cloud, mist or fog, that is much acidic compared to rainwater. These droplets are deposited on the forest canopies, a process that is called ‘occult deposition’. Most of the N02 and S02 produced in Scotland come from large industrial units and power stations, but vehicles are another significant source of nitrogen and oxides. Having said this, let us find out how this acid deposition affect the forests in Scotland (Acid Rain).
It is well established that when acidic rain interact with the tree canopy forming the forest, the chances of becoming more acidic increases due to leaching of foliage’s organic acid anions or dry deposition that have accumulated. Alternatively, the plant tissue may experience a situation where acid precipitation undergoes an exchange process where H+ is exchanged for base cation. Here, the foliage close to 80% proton deposition. This explain why direct injury to the foliage is witnessed more in areas close to the source of pollution i.e. large industries. In these areas, acid deposition caused the leafy plants to accumulate large amounts of toxic substances like mineral cadmium. Studies conducted have also established that acidic accumulation on leaves of the forest tress interfered with the production of carbohydrates during photosynthesis leading to what has been termed defoliation. Defoliation is a state where green leaf material dies off causing the plants to starve to death since they no longer have leaves to provide the needed carbohydrates. The effect of acidic rain on the forest tress of Scotland followed certain factors. Some of the trees appeared to be better adapted to environmental stress; the trees type, leaf structure and height influence the forest vegetation ability to adapt to the harsh conditions of acidic rain (Hunter). It is generally said that acid rain directly harm the forest tress through leaching calcium ions from their foliage. On the other hand, it indirectly harm the tress by interfering with their ability to tolerate stresses in their niche. For instance, one study by EPA revealed that acid rain impairs the trees’ winter hardening process, making them vulnerable to damages associated with the cold weather. Still some trees are damaged in their roots by the acidic rain that moves through the soil releasing toxic aluminium ions.
Far places (those not close to sources of pollution) experience indirect injury that include acidification of soils and rivers flowing through the forests. With regard to the forest soil, acid rain affect the vegetation by changing the soil chemistry. Such is the case that acidic rain progressively cause the soil to lose important nutrients like potassium, magnesium, and calcium. Consequently the soil record high concentration of dissolved inorganic aluminium that poison the forest vegetation. Nitrogen accumulation in the forest soil further interferes with the capacity to retain other nutrients needed for proper growth. “Valuable nutrients such as calcium and magnesium are normally bound to soil particles and are, therefore, protected from being rapidly washed into groundwater. Acid rain, however, may accelerate the process of breaking these bonds to rob the soil of these nutrients. This, in turn, decreases plant uptake of vital nutrients” (Stewart, 170- 180). Forest vegetation that lack these important nutrients become more vulnerable to pest invasion, climatic extremes and the impacts of other pollutants like Ozone.
Acid rain effect on the Scotland forests relates to the disruption of soil regeneration according one recent research. Here, Soil regeneration has much to do with the recycling of minerals nutrients and chemicals through animals and plants back to the earth. It is also believed that acids interfere with the decay of organic matter that is much essential in enriching the soils.
In conclusion, the effect of acid rain on the forests in Scotland is undeniable. As a country once covered with vast land of forest, it has witnessed a significant destruction of forest vegetation due to acidic rain. Most of the N02 and S02 produced in Scotland come from large industrial units and power stations, but vehicles are another significant source of nitrogen and oxides. Once dissolved in rainwater, these oxides form harmful pollutants after mixing with other chemicals present in the atmosphere. The resulting pollutants either settle on forest trees as ‘dry deposition’ or washed off into the forest soil as ‘wet deposition’. The most common manmade acids in rain are nitric (HNO3) and sulphuric (H2SO4) acid.
- Acid Rain. 1st ed. Dordrecht: Springer Netherlands, 1983. Print.
- Hunter, Philip. “Restoring Tropical Rain Forests”. EMBO reports (2017): e201744118. Web.
- Read, Jennifer, and Tanguy Jaffré. “Population Dynamics Of Canopy Trees In New Caledonian Rain Forests: Are Monodominant Nothofagus (Nothofagaceae) Forests Successional To Mixed Rain Forests?” Journal of Tropical Ecology 29.06 (2013): 485-499. Web.
- Stewart, Philip J. “Air Pollution, Acid Rain and The Future Of The Forests”. Land Use Policy 2.2 (1985): 179-180. Web.