Tebaran, a hunter in Borneo, sees a difficult future for indigenous people as logging operations engulf the rainforest that was the land of his ancestors. Tropical rainforests are also critical biomes that regulate Earth’s resilience. Cutting down too much of a rainforest, combined with the warmer and often drier environment that climate change is expected to bring in the tropics, may cause an abrupt tipping point in the ecosystem, turning the rainforest into a savannah. If that were to happen, it could have damaging impacts on local freshwater supplies and trigger a massive loss of carbon.
Thanks to a boom in construction projects like this one in Hong Kong, cities around the world continue to expand. According to projections, two thirds of the cities we will need by 2030 have not been built yet. This is a gigantic challenge but also a grand opportunity. We now know how to build cities that integrate ecosystems into their design to make them attractive, resilient, and healthy. Nature plays a key role in the design of sustainable cities.
A pair of putty-nosed guenon, tree-dwelling monkeys, are offered for sale as bushmeat by poachers along a road in Cameroon. European fisheries policy may have unintentionally stimulated an increase in bushmeat hunting. When foreign fishing fleets were pushed away from European waters by new regulations, the big ships moved off the coast of Africa, where they cleaned out fish resources. That put small-scale African fishermen out of business. To make ends meet for their families, some of these fishermen became bushmeat hunters. The killing of these animals not only threatens biodiversity in the region, it also increases the risk of zoonotic disease outbreaks, such as happened with Ebola.
When lakes and rivers are loaded with chemicals from urban and agricultural runoff, algae blooms can choke the water. Under such circumstances, the water can become so oxygen-deprived that fish cannot live in it. As we have increasingly discovered, safeguarding rich fish populations is critical to enabling marine environments such as lakes and coral reef systems to bounce back after environmental shocks. Following a major bleaching event, for example, a coral reef system can break down. But the presence of many varieties of grazing fish, such as parrot and surgeon fish, can help the reef regenerate itself. Without these aquatic “lawnmowers,” a collapsed coral reef will be taken over by seaweed. If the system, moreover, is loaded with nutrients from agricultural runoff, it is even more likely to get stuck in a new murky, algae-dominated state.
Mangrove trees along the coast of West Papua provide nursery habitat for fish in their root systems. As shown recently by The Economics of Ecosystems and Biodiversity (TEEB) initiative, mangrove systems provide significant incomes for small-scale coastal communities if kept intact. By contrast, if sudden extreme flooding events degrade mangroves, the resulting loss of livelihoods can have devastating social costs.
What does the future hold for a boy in Rwanda? Sustainable solutions offer the best chances to alleviate poverty. The key challenge in exploring sustainable food systems within planetary boundaries is to recognize that the era of farmland expanding into natural ecosystems has come to an end. We must now feed humanity on existing farmland, which will require sustainable intensification. This, in turn, will necessitate major innovations, combining cutting-edge science with indigenous knowledge.
Orderly ranks of oil palms have replaced natural habitats for plants and animals in Sarawak. Since the 1980s and 1990s, forests in this part of Borneo have been leveled at an unparalleled rate. More tropical wood has been exported from Sarawak and the rest of Borneo during the past two decades than from Africa and South America combined. As logging concessions have expired, the land in many places has been converted to palm oil plantations, encouraged by subsidies from the government. Since the 1990s there has been a 40-fold increase in planned plantations. The largest palm oil plantation in the world, encompassing 800,000 hectares, has now been proposed on Borneo.
A rapidly changing environment puts these social–ecological systems at risk. At the same time they can teach us a lot about how to work with nature for human wellbeing and resilience.