To Chop, or Not to Chop? The Issue of Exotic Invasive Trees in the Western Ghats

To Chop, or Not to Chop? The Issue of Exotic Invasive Trees in the Western Ghats

The Forest Department of Tamil Nadu must respond to a petition submitted to the Madurai High Court for the Forest Department to take action to resolve the problem. This problem has been brewing for more than 50 years, and there is no simple solution. I defined the problem, its complexity, and some interventions that help guide responses to court orders in the short term and possibly solve the problem in the long term.

The problem

Initially, these non-native trees were planted in small quantities to meet the growing demand for fuelwood. Around the time of India’s independence, the department began to expand the area of ​​these plantations to meet the growing demand for tanned bark in the tanning industry and the demand for wood pulp in the paper industry (trade sanctions against South Africa ceased after India’s independence). The supply of tanned bark in South Africa is the main reason for the increase in demand for tanned bark). What followed was a tree-planting fever, and by 1988, more than 11,000 hectares of grassland had been converted into plantations. These plantations have been actively harvested for more than 40 years, but in the mid-1990s, the forest sector stopped this activity. The main reason for this policy change is that the forest sector is increasingly aware that it is not a good idea to convert natural ecosystems into non-native single plantations. When plantation harvesting ceases, exotic trees have an unfair advantage over grass in terms of resources (soil nutrients and water) and continue to spread and encroach on grasslands. The invasion was so successful that only a few grasslands remained on the Parni Mountain. The old sholagrassland landscape of Palni Hills has been completely replaced by the sholaexotic plantation landscape. This large-scale landscape transformation has affected the ecology of the landscape and affected animals that depend on grasslands for resources, especially food, which is very natural.

The three non-native invasive trees

There are three main invasive alien species that must be addressed: acacia (Acacia mearnsii), eucalyptus (Eucalyptus globulus), and pine (Pinus patula). The wattle was first introduced for firewood and later to satisfy the demand for tanned bark; the introduction of eucalyptus and pine was mainly to satisfy the demand for wood pulp. Facts have shown that acacia is the main invasive tree species in the area, which is not surprising, since it is considered one of the most invasive tree species in the world. The spines are so dense in some areas that people claim to have found the carcasses of deer, which appear to have starved to death after trying to get caught in the dense bushes of young spines. As we all know, eucalyptus absorbs a lot of water to support its rapid growth, which is detrimental to the groundwater level. There is evidence that acacia and eucalyptus trees are under drought pressure, which suggests that some patches of these species may collapse after the initial boom phase, reaching high densities that lead to harmful competition and resource depletion. There is evidence that the fungus is killing, or at least preventing the growth of many acacia trees. Shola trees have been successfully planted in plantations of all three species; some shola trees seem to have done so nearly 50 years ago. It should be pointed out that although exotic trees have invaded the grassland, they have not successfully invaded the shoal forests. Acacia trees are best killed by cutting their stems in places with lower underground wood density. Eucalyptus is difficult to remove because they can be regenerated from cut stumps, and their roots are usually very extensive, sometimes up to a hundred Many feet, and pine trees are the easiest to kill. The acacia tree needs the most attention due to its expansion, but it is also the firewood tree of choice in the area.

Is there a solution?

The petition submitted to the court requires the Forest Department to remove invasive alien trees to restore the grasslands. The general idea to achieve this goal is simple: cut down the invasive trees and the grasslands will return. Although very little is known about the exact mechanism for establishing the sholagrassland ecosystem, there is hardly any debate that this process will take hundreds or even thousands of years. More than 40 years of intensive planting activities and the subsequent 20 years of widespread invasion of non-native trees have undoubtedly significantly changed the soil and groundwater levels in the area. So, is it reasonable that a system that has undergone thousands of years of evolution but has undergone large-scale modifications over more than 60 years can be easily restored to its previous state? Is this reasonable? The short answer to this question is "probably not", so we must realize that we are dealing with a complex problem that may require more than a simple solution to cutting down invasive trees.

What do we do?

There is no clear answer to the recovery process. Any management intervention must be implemented with care and patience, and initially on a small scale. The landscape is variable, which means that different parts of the landscape should be given different levels of priority and intervention. The long term must be taken into account: the transformation of the landscape has lasted 60 years and we have waited 20 years for the plantation activities to end before intervening. Therefore, we must be patient with the recovery process and not expect large-scale changes in the short term. Any tree felling should take into account the local residents' demand for firewood, whether it is for cooking or heating. Unless some efforts are made to reduce the local people’s dependence on fuelwood for hundreds of years in the region, we cannot expect this dependence to disappear anytime soon. Fortunately, the Mukurthi Wildlife Sanctuary in Niligiri Hills and the Kodaikanal Wildlife Sanctuary in Palni Hills provide the department with ample opportunities to try management interventions while meeting the needs of locals who use the buffer zone for firewood. In order for the grassland to return, they need our help and strong long-term commitment.

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