Living world (ecosystems, rainforests, hot deserts/cold environments)

In the Amazon rainforest in Brazil, deforestation has brought clear economic benefits. Cattle ranching is the biggest cause of clearance¹, and Brazil has become one of the world's largest beef exporters, earning export income and providing jobs on ranches and in meat-processing plants. Large areas have also been cleared for soya, which is exported as animal feed. Mining, such as the huge Carajás iron ore mine, and hydroelectric dams such as Belo Monte on the Xingu River provide raw materials and electricity for Brazil's growing industries and cities. Roads like the Trans-Amazonian Highway, begun in the 1970s, opened up the region for settlers. For an NEE, these activities help pay off debt and raise national income².

However, the environmental costs are severe. The rainforest is the most biodiverse ecosystem on Earth, so clearing it destroys habitats and threatens species with extinction before some have even been studied. Once the trees are removed, there is no canopy to intercept heavy rainfall and no roots to hold the soil, so the thin, nutrient-poor soil is quickly eroded³ and washed into rivers. Because so much rainfall in the Amazon is recycled through transpiration⁴, removing trees makes the local climate drier, which increases the risk of drought and forest fires. Globally, burning and clearing forest releases stored carbon as carbon dioxide, adding to climate change, and some studies now suggest parts of the south-eastern Amazon release more carbon than they absorb.

Weighing these up, the benefits are real but they are short-term and unevenly shared⁵. Much of the profit goes to large landowners and companies, while indigenous communities lose land and resources and some were displaced by Belo Monte. Cattle pasture on eroded soil becomes unproductive within a few years, so the economic gain itself does not last, whereas the loss of biodiversity is permanent. The costs are also felt by the whole world through climate change. On the other hand, Brazil showed that it can reduce clearance while its economy grows: annual deforestation fell from about 27,800 km² in 2004 to about 4,600 km² in 2012⁶ through stronger enforcement and protected areas, suggesting the benefits do not require such large losses.

Overall, I disagree with the statement⁷. Deforestation brings important income to Brazil, but the environmental costs are long-lasting, global and often irreversible, while the benefits are temporary and go to a minority. A more sustainable approach, using selective logging, ecotourism and enforced protection, could keep much of the economic value without the environmental damage.

Hot deserts receive less than 250 mm of rain a year¹, daytime temperatures can exceed 40°C and nights can be cold, so living things must save water and cope with heat.

Cacti such as the saguaro have thick, fleshy stems that swell to store water after rain, so the plant can survive long dry periods. Their leaves have been reduced to spines, which lowers the surface area for transpiration and so reduces water loss², while also stopping animals eating the plant for its moisture. A waxy coating on the stem further reduces evaporation. Many cacti have shallow but very widespread roots that quickly absorb rain before it evaporates, whereas plants such as the mesquite tree have very long tap roots that reach groundwater³ deep below the surface. Ephemeral plants survive as seeds for long periods, then germinate, flower and set seed within a few weeks after rain, so they avoid the driest conditions completely⁴.

Camels store fat in their humps⁵, which can be broken down for energy when food is scarce, and they can tolerate losing a large proportion of their body water, so they can travel long distances without drinking. Long eyelashes and nostrils that can close protect them during sandstorms. The fennec fox has very large ears that radiate heat away from its body, helping it stay cool, and it is nocturnal, hunting in the cooler night and sheltering in burrows during the heat of the day, which reduces water loss through sweating and panting⁶.