In pre-human times, almost all of New Zealand was covered in forest, with the exception of high mountain areas. Māori settlers began to clear forest, and by the time the first Europeans arrived in New Zealand, up to 40% of the original forest cover had gone.
Early European settlers used timber for housing and fuel. They also felled large areas of kauri forest to export the high quality timber. Many of the trees they logged where over a thousand years old! Forests were also burnt off to provide land for farming. Only 25% of New Zealand is now covered in native forest.
Native forests are of great importance to New Zealand as a habitat for unique birds and plants and as part of our cultural identity. The forests are also a resource for recreation and as a tourist attraction.
Forested areas support a huge variety of wildlife, from fungi and lichens, to plants, insects and animals. Deforestation results in loss of habitat, as well as the possibility of extinction of a huge variety of wildlife and loss of biodiversity. Organisations such as the Ministry of Agriculture and Forestry and the Department of Conservation are involved in management of New Zealand’s native forest to protect it from logging, damage through fires or loss of biodiversity caused by introduced mammals such as rats, possums and deer.
Forested areas slow the flow of water, allowing it to soak into the soil and into underground water channels. When trees are removed, water is unable to soak into the soil and, instead, runs off the surface at a faster rate. This can cause localised flash floods and erosion, particularly in mountainous regions. Pollutants are also easily washed into waterways.
Tree roots form an underground network that stabilises the soil, so deforestation often leads to increased soil erosion. Soil and nutrients are washed off the land and into waterways, changing the quality of the water and affecting wildlife. Eroded land that has lost topsoil can quickly become barren wasteland, as it is not as productive for crops. This land may be abandoned while further areas are deforested.
Nature of science
An ecosystem is made up of living things, the environment they live in and the interactions between them. The removal of part of the system has an effect on the rest of the system. For example, removing trees may also affect soil stability, water quality and biodiversity.
Deforestation threatens to contribute to climate change by reducing the Earth’s ability to control the level of the major greenhouse gas CO2 in the atmosphere. Plants absorb CO2 during photosynthesis, and large forest areas can absorb vast amounts. Without forests, the CO2 is not absorbed and, therefore, goes straight into the atmosphere.
Explore the interactive Land use – impacts on waterways, this has a focus on farming and land development.
In the Connected article Trees, seas and soil discover what a carbon sink is and why they are so important.