Natural forests have been an integral part of humanity since time immemorial because of the numerous ecosystem services they offered for the existence of humankind. Its major interest is the providing of raw material in the manufacturing industry.
Timber harvesting has always been practiced on a small scale mostly for domestic purposes. However, over the years, the coming in of industrialization and globalization has resulted in the increase in trade. The globalized trade has increased markets which resulted in the demand for timber products especially round wood.
The round wood has become the major drive for deforestation of natural forests through logging and land clearing for the expansion of plantation forests in order to meet demand for timber. The demand in round wood is estimated to reach six million cubic by 2050. This means that more forest areas will be lost to timber harvesting and clearing for the expansion of industrial plantations.
Timber harvesting in general has negative impacts on the environment and biodiversity. However, commercial timber harvesting causes more impacts because it is done on a large scale and involves a lot of activities. The impact and extent on biodiversity loss varies significantly depending on the geographic variability, type of harvesting system (clear cut or selective cutting) being applied in that area and the technology being used.
Commercial harvesting involves the felling and extraction of timber using heavy equipment such as skidders, teleloggers, and tractors. It also involves the clearing of land for the creation of roads for accessibility and landings where logs are kept before transportation. Other indirect impacts of timber harvesting include noise from equipment such as chainsaws and saw mills, oil spillages and fuel leaks from machinery. All these disturb the ecosystem functions.
Natural forests harbour the greatest species diversity with most species being found in Tropical Rainforests or Amazon Forests. These forests are ecologically sensitive biomes with very high endemism and fragile in nature. Brazil and Indonesia are home to the Tropical Rain forests are amongst the leading countries in the production of forest products.
One of the leading causes of biodiversity loss in the Amazon forests is commercial timber harvesting which results in the cutting down of trees which are important habitats for animals and birds. Timber harvesting causes habitat destruction. Habitats play a crucial role in the survival of species as they provide food, shelter and security. Without habitats, species become vulnerable and susceptible to all forms of danger. Clearing of trees also leads to habitat fragmentation which can eventually lead to extinction of species.
In Zimbabwe, 90% of plantation forestry is found in the Eastern Highlands. Natural forests in Nyanga, Chimanimani, Vumba and other areas were cleared for monoculture stands of trees such as Pinus and Eucalyptus species. Firstly the clearing of land affected the diversity of both flora and fauna which included endemic species. A reduction in biodiversity has been noted. Studies carried out in the Eastern Highlands showed that diversity of bird species is higher in natural forests as compared to plantations.
Commercial harvesting also occurs in the Kalahari sand forests or Zambezi Teak forests, Matebeleland North and Midlands Provinces of Zimbabwe are home to Teak, Mukwa and Mahogany. These tree species grow on the fragile Kalahari sand soils and timber harvesting has been the greatest threat which has significantly disturbed this ecosystem and resulted in the loss of biodiversity.
The long term effects of timber harvesting on the ecosystem is that it compromises the resilience of forests which affects their long term ability to provide ecosystem services. Microclimatic conditions are maintained by forests and natural forests influence temperature, light and humidity of an area. The microclimate enables the creation of microhabitats for climate sensitive species. The destruction through logging of these forests leads to loss of these species. Secondary impacts of commercial timber harvesting which indirectly leads to biodiversity loss include invasive species for example the spread of black wattle in the Eastern Highlands of Zimbabwe, increases risks of fire and climate change as a result of reduced carbon sinks.
Global population will continue to increase and so will the demand for timber. This means that plantation forestry remains an economically viable industry which will continue to threaten biodiversity. Good conservation and biodiversity standards now need to be ensured in timber harvesting operations so as to mitigate the loss of biodiversity by implementing reduced impact logging aimed to strike a balance between economic and environmental sustainability.
Interesting facts
- 300 000 ha of indigenous hardwood of forests are lost annually in Zimbabwe
- Tree cover the size of a football pitch is lost every 6 seconds in the Tropical Rainforests
- The Amazon rainforest might dry out if 25% of tree cover is lost
