Case Study Deforestation

[Jacquelyne Betance]

Humansfirst discovered the Amazon rainforest about 13,000 years ago. But, it was the arrival of Europeans in the late 15th century that spurred the conversion of the forest into farmland. Nevertheless, the sheer size of the Amazon meant that the rainforest remained largely intact until the early 20th century. It was in the latter half of the 20th century that things began to change.9

Industrial activities and large-scale agriculture began to eat away the southern and eastern fringes of the Amazon, from the 1950s onwards.10 Deforestation in Brazil received a significant boost in 1964 when a military dictatorship took power and declared the jungle a security risk.11 By the 1970s, the government was running television ads encouraging land conversion, provoking millions to migrate north into the forest.12 Settlements replaced trees, and infrastructure began to develop. Wealthy tycoons subsequently bought the land for cattle ranches or vast fields of soy.13

For its three million plant and animal species and one million Indigenous inhabitants, it is imperative that Amazonian deforestation is massively and immediately reduced.21 As much as 17 per cent of the Amazon has been lost already.22 If this proportion increases to over 20 per cent, a tipping point will be reached.23 This will irreversibly break the water cycle, and at least half of the remaining forest will become savannah.24

Losing the Amazon would also mean losing the fight against climate change. Despite the rampant deforestation in recent years, the remaining Amazon rainforest still absorbs between 5 to 10 per cent of all human CO2 emissions.25 Cutting trees down increases anthropogenic emissions. When felled, burned or left to rot, trees release sequestered carbon.26 A combination of reducing greenhouse gas emissions and preserving existing forests is crucial to preventing dangerous levels of global warming.27

Compared to the Amazon and Southeast Asia, deforestation in the Congo Basin has been low over the past few decades.35 Nevertheless, great swathes of primary forest have been lost. Between 2000 and 2014, an area of forest larger than Bangladesh was destroyed.36 From 2015 until 2019, 6.37 million hectares of tree cover was razed.37 In 2019 alone, 475,000 hectares of primary forest disappeared, placing the DRC second only to Brazil for total deforestation that year.38 Should the current rate of deforestation continue, all primary forest in the Congo Basin will be gone by the end of the century.39

80 million people depend upon the Congo Basin for their existence. It provides food, charcoal, firewood, medicinal plants, and materials for building and other purposes. But, this rainforest also indirectly supports people across the whole of sub-Saharan Africa. Like all forests, it is instrumental in regulating rainfall, which can affect precipitation hundreds of miles away. The Congo Basin is a primary source of rainfall for the Sahel region, doubling the amount of rainfall in the air that passes over it.46

It would also be devastating for biodiversity. The Congo Basin shelters some 10,000 animal species and more than 600 tree species.48 They play a hugely important role in the forest, which has consequences for the entire planet. For instance, elephants, gorillas, and other large herbivores keep the density of small trees very low through predation.49 This results in a high density of tall trees in the Congo rainforest.50 Larger trees store more carbon and therefore help to prevent global warming by removing this greenhouse gas from the atmosphere.51

Preserving the Amazon and Congo Basin rainforests is vital for tackling climate change, as these deforestation case studies demonstrate. We must prioritise protecting and enhancing our existing trees if we are to limit the global temperature increase to 1.5C, as recommended by the IPCC.52

Rainforests are incredibly complex ecosystems, but understanding a few basics about their ecology will help us understand why clear-cutting and fragmentation are such destructive activities for rainforest biodiversity.

High biodiversity in tropical rainforests means that the interrelationships between organisms are very complex. A single tree may house more than 40 different ant species, each of which has a different ecological function and may alter the habitat in distinct and important ways. Ecologists debate about whether systems that have high biodiversity are stable and resilient, like a spider web composed of many strong individual strands, or fragile, like a house of cards. Both metaphors are likely appropriate in some cases. One thing we can be certain of is that it is very difficult in a rainforest system, as in most other ecosystems, to affect just one type of organism. Also, clear cutting one small area may damage hundreds or thousands of established species interactions that reach beyond the cleared area.

Many factors contribute to tropical deforestation, but consider this typical set of circumstances and processes that result in rapid and unsustainable rates of deforestation. This story fits well with the historical experience of Brazil and other countries with territory in the Amazon Basin.

Population growth and poverty encourage poor farmers to clear new areas of rainforest, and their efforts are further exacerbated by government policies that permit landless peasants to establish legal title to land that they have cleared.

At the same time, international lending institutions like the World Bank provide money to the national government for large-scale projects like mining, construction of dams, new roads, and other infrastructure that directly reduces the forest or makes it easier for farmers to access new areas to clear.

The activities most often encouraging new road development are timber harvesting and mining. Loggers cut out the best timber for domestic use or export, and in the process knock over many other less valuable trees. Those trees are eventually cleared and used for wood pulp, or burned, and the area is converted into cattle pastures. After a few years, the vegetation is sufficiently degraded to make it not profitable to raise cattle, and the land is sold to poor farmers seeking out a subsistence living.

Regardless of how poor farmers get their land, they often are only able to gain a few years of decent crop yields before the poor quality of the soil overwhelms their efforts, and then they are forced to move on to another plot of land. Small-scale farmers also hunt for meat in the remaining fragmented forest areas, which reduces the biodiversity in those areas as well.

Another important factor not mentioned in the scenario above is the clearing of rainforest for industrial agriculture plantations of bananas, pineapples, and sugar cane. These crops are primarily grown for export, and so an additional driver to consider is consumer demand for these crops in countries like the United States.

These cycles of land use, which are driven by poverty and population growth as well as government policies, have led to the rapid loss of tropical rainforests. What is lost in many cases is not simply biodiversity, but also valuable renewable resources that could sustain many generations of humans to come. Efforts to protect rainforests and other areas of high biodiversity is the topic of the next section.

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Initial soil wetness of the following experiments: 1) the 37 subexperiments of the soil wetness case (18 dashed lines plus the solid line); 2) rainfall experiment/dry season case and river breeze experiment, which used field observations (solid line); and 3) rainfall experiment/wet season, which used the wettest profile (dashed line). The highlighted height is the pasture root depth (100 cm), mentioned throughout the discussion of soil moisture case results.

Mean horizontal wind speed/magnitude (at 400-m height) for the CTL case in the (a) dry season and (b) rainy season. The rectangle shows the deforestation area (AREA2W), which suggests how the wind direction coincides with the longer side of the rectangle.

Percentage difference in rainfall as a function of deforested area for (a) the zones where the rainfall increased (lines with positive values) and the zones where the rainfall decreased (lines with negative values) and for (b) the entire deforested area.

The Amazon region has been threatened in the last 50 years by continuous deforestation promoted by road construction and fostered by rising demands for timber, beef, and soybeans (Hutyra et al. 2005; Nepstad et al. 2008). Notably, the regions in eastern and southern Amazonia (the arc of deforestation) are under higher pressures (Figure 1), leading to increasing susceptibility to fire and ecosystem collapse.

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