Thomas E. Lovejoy
The ride had started in the pitch black dark of 4:00 in the morning - driving north through the forest on the highway to far distant Venezuela. Not long after 6:30, after a walk in from a muddy side road and a climb of 40 meters I emerged atop a tower with a view in all directions of unbroken forest canopy.
There was so much green that at first it seemed a blur, but that quickly dissolved into a mosaic of individual tree crowns in more shades of green and with more shapes of leaves than one ever imagined could exist. I strained - mostly unsuccessfully - to find matching tree crowns. This was primeval Amazon rainforest brimming with myriad life forms - and to the novitiate: partly heard, and mostly not seen.
My eye continued searching for possible repetition of leaf types that could indicate two trees might be of the same species, and my ear was distracted by many sounds (birds, and other - mostly unknown to me). Yet what was truly striking were dozens and dozens of plumes of moisture emerging from the forest canopy - the consequence of rains that had just preceded us. The amazing hydrological cycle of the Amazon was temporarily visible.
Weather moves from east to west in the Amazon. That led Brazilian scientist Eneas Salati and colleagues in the mid-1970s1 to examine ratios of oxygen isotopes in rainwater sampled from the Atlantic coast to the Peruvian border. They revealed the Amazon produces half of its own rainfall by recycling moisture several times before reaching the high wall of the Andes. There, air masses rise and cool and the moisture precipitates out into the 20% of the world’s river water that forms the Amazon river system.
Shattered lay the old dogma that vegetation was simply the consequence of climate and had no influence on it whatsoever. The initial moisture arriving from the tropical Atlantic falls as rain. Most of it returns to the westward moving airmass through evaporation from the complex surfaces of the forest and transpiration through the leaves – in part revealed by the plumes of moisture that emanate from the forest after rainfall. Farther west it falls again as rain and the cycle repeats itself.
Image caption: View from the tower at INPA’s field site on the ZF-3 road about 40 km north of Manaus. Photograph taken at 40 meters high by Marisa Pandolfo.
At that time, this revelation raised the question of how much deforestation could cause the hydrological cycle to degrade because it is so driven by trees and leaves. There was no way to immediately answer that question and while the extent of deforestation that could trigger it seemed very far off, it was clear the future of the Amazon depends very much on maintaining the integrity of the cycle.
Today almost a half century later we know much more about the hydrological cycle and its importance not only for the Amazon but also for every country in South America except Chile (which lies in the rain shadow west of the southern Andes). Beyond being critical for the Amazon and a significant portion of terrestrial biodiversity, it also benefits agriculture in Central Brazil and farther south and contributes to urban reservoirs. It is clearly an integral part of the South American climatic system and needs to be respected and treated with great care2 and 3.
The immediate lesson is that the Amazon and its great forest have to be managed as a system and that individual decisions must be made within that context. The staggering Amazon river system needs to be treated similarly. Immensely large sediment loads are carved off the Andes annually and carried by a number of the rivers. The rivers flood so extensively that they overflow their banks and flood the adjacent floodplain forest, providing life-giving nutrients from the freshly weathered rocks of the mountains.
Together with the permanent wetlands, the flooded forests constitute 20% of the entire Amazon. They are also of huge importance for a number of fish species which depend on feeding in the adjacent floodplain forests and thereby benefit from a significant transfer of nutrients from the terrestrial to the aquatic ecosystem.
There are a number of large catfish species the life cycles of which range from the estuary to the headwaters. They are an important source of animal protein for local populations. That of course can be severely disrupted by large hydro-electric installations, whereas run-of-river designs can protect their migratory pathways.
The Amazon as a whole is renowned for the greatest concentration of biodiversity on Earth, so it is not surprising that the river system itself has an estimated 3,000 species of fish -- more than any other river system in the world4. In addition to the large catfish, and the specialists which use floodplain forests at the time of high water, they include the aquarium fishes, essentially little jewels with fins. Today those are harvested from the wild in a sustainable fashion.
The Amazon has an estimated 15,000 species of trees, and there are currently 1300 described species of birds5. There are many spectacular birds and plenty of remaining mysteries like the Diademed Parrot (Amazona diadema) which has a fairly small range and can regularly be seen near the tower at the start of this essay – but completely disappears for three months a year.
New bird species are being described on a regular basis with real surprises like the first jay recorded in the southwestern Amazon lowlands (in islands of grassy habitat within the forest). Birds endemic to the extensive forests between the large tributaries long described as subspecies turn out to be full species: the very similar forms sing distinctive songs on opposite sides of major tributaries and have been elevated to distinct species.
Image caption: The Campina Jay (Cyanocorax hafferi) was discovered and described recently from remote savanna enclaves deep in previously unexplored parts of the Amazon. Photograph by Kevin J. Zimmer.
Not all Amazon tributaries carry heavy sediment loads but almost all those that originate in the Andes do. Those sediments are of fundamental importance to floodplain agriculture which provides a stark contrast to the destructive forms of agriculture based on deforestation (cattle and soy). There is a system of “pulse-agriculture” – of quite some antiquity - that takes advantage of annual deposits of fresh silt during the lower water months of year. Run-of-river hydro-electric dams can protect these agricultural systems as well.
Not long after the arrival of Europeans in the Amazon, as elsewhere in the Americas, indigenous populations crashed from the introduced pathogens. Before that happened, however, the chronicles of Francisco de Orellana’s6 expedition in the first part of the 16th century show they were scarcely ever out of view of native settlements as they made their way down the river. Yet the earlier accounts receded from public memory and only recently has the extent of indigenous occupation and the sophistication of their use of Amazon biodiversity in support of their well-being become clear.
Even so it is likely that the majority of that population was never far from the rivers which were the means of transport as well as an important food source (primarily fish). Their agricultural systems also included ones where they enriched the soils. They created localized very fertile “terra preta” (black soils) which maintain their fertility to this day.
I remember quite clearly my first impression of the Amazon rainforest in June 1965, namely just endless green -- and where were the animals? For a moment it was disappointing, puzzling, and not living up to the diversity for which it is famous. Gradually it became clearer how complex in structure it is and how most animals behave cryptically to avoid predation. Soon one’s eye, ears and mind adjust and you begin to see elements of the myriad detail. Some of the first things that catch one’s attention are insects. A flash of iridescent blue of a fleeting Morpho butterfly perhaps.
The famous biologist and ant specialist Edward O. Wilson once said to me he wanted to go to “the serious tropics”. That is how I came to host him at my research project in the central Amazon. I decided to accompany him for his first day and evening to try to see the forest from his perspective. It was a revelation. It was as if he possessed the ant and termite equivalent of the Midas touch: literally everywhere he stopped to look there were ants and termites, bearing out the statement that there is more biomass of ants and termites than any other kind of animals in the rain forest. It was capped off by an evening march of leaf-cutting ants, each carrying a green “sail” of a leaf fragment destined to become mulch in the colony’s underground fungus farm.
Many Amazon species occur at very low densities and essentially are always rare. Yet there are so many rare plants and animals that the odds are that one will see some of them. One time late in the afternoon I was walking on the trail to my favorite camp when I caught the fluttering of a butterfly out of the corner of my eye. A Morpho I thought, but a few steps later I realized it wings were not beating like a Morpho. So I followed what I first thought was a very large pale butterfly until it landed on a tree trunk. Then I was able to see that it was an enormous speckled white moth. It was in fact one of the largest moths and exceedingly rare: known as the White Witch (Thysania agripinna) it is so rare that its caterpillar stage has yet to be described by science.
The Amazon is the single greatest repository of terrestrial biological diversity. It is close in dimensions to the 48 contiguous United States. It also has a tremendous stock of carbon – perhaps 100 billion tons (including soils)7. Keeping that in the Amazon is essential from a climate change perspective. Yet to value the Amazon for its carbon is like valuing a computer chip for its silicon. The world needs the Amazon for its biodiversity and its carbon.
The Amazon was pretty sparsely settled in the centuries after European discovery, and was mostly territory for exploring naturalists and religious figures interested in converting the indigenous peoples (a process that continues to this day). It became largely occupied by mixed-origin people who were quite skilled and knowledgeable about how to put together an existence based to a great degree on knowledge acquired from the original indigenous peoples.
The Amazon had a brief moment in the spotlight when Goodyear’s discovery of vulcanization transformed rubber into a highly useful product - good for bicycle and automobile tyres and more. Basically, all rubber came from the Amazon from a tree (Hevea brasiliensis) that was naturally dispersed through the forest to minimize impacts of natural diseases. For a few decades the Amazon countries and particularly Brazil had the global monopoly on rubber production.
Manaus, 1000 km upriver became one of the wealthiest cities in South America. A friend of mine from the port city of Belem had a grandfather who shipped his stiff collars to Paris to be starched. In 1876 seeds were shipped by Henry Wickham to the world center of economic botany, namely the Royal Botanic Gardens at Kew. They became the basis for the entire southeast Asian rubber industry. There in the absence of natural enemies it was able to grow rubber trees in plantation form and undercut the Amazon market.
The Amazon is actually part of nine different countries and for all of them, it has always been a frontier, maybe a place for science, a place for extracting resources like Brazil nuts, but not offering much in the way of economic opportunity. Starting in the 1960s, particularly in Brazil, a mindset developed that it would be smart to occupy the Amazon to prevent some other power from doing so.
Most of the large highway (e.g., trans-Amazon highway system) and hydro-electric projects date from that time. I believe a lot of what transpired would not have stood up to thorough economic scrutiny. Most proceeded using government funding and led to widespread unintended consequences of spontaneous deforestation and colonization starting with the very first, the Belem-Brasilia highway between the port city and the new capital. There has been more forest destruction in Brazil than in other Amazon countries, although the challenge exists in all of them.
Starting in the 1990s with the G-7 pilot program for the Brazilian Rainforests, major international funding managed by the World Bank became available to encourage more sustainable trajectories in the Amazon. Brazil having invited the Earth Summit to take place in Rio de Janeiro in 1992 began giving higher priority to the environment, biodiversity and the Amazon.
In 1965 there was just one national park in the Amazon (Canaima in Venezuela) and one demarcated indigenous area (The Xingu in Brazil). Today about half of the entire Amazon is under some form of protection roughly equally divided between standard conservation areas and demarcated indigenous reserves. Norway and Germany in particular underwrote an Amazon fund to assist in reducing deforestation and developing sustainable alternatives. The World Wildlife Fund and the World bank put together two major funding packages (The Amazon Region Protected Area Program = ARPA, and then ARPA 2) to assist Brazil in setting up and managing these areas. Whatever the imperfections it is a remarkable achievement.
The current Brazilian government tends mostly to see the forest and its biodiversity as of little value compared to economic activities like cattle, soy (referred to as bio-economy) or mining. In contrast, the Amazon’s highest value is in development that is based on forest biodiversity, and in maintaining the hydrologic cycle for the Amazon and the South American climate system.
The latter has become a critical matter. What at first seemed an unbelievably distant possibility of a tipping point where the hydrological cycle would no longer function normally is right at hand. Deforestation which originally seemed the sole driver needing to be managed is now interacting synergistically in negative ways with climate change and the extensive use of fire8.
It has been clear for quite some time that the southern and eastern Amazon are vulnerable to conversion to savannah-like vegetation with enormous loss of biodiversity and value to local people. The same drying trend that would cause that will also lead to diminished water supplies for hydro-electric projects in that part of Brazil.
Carlos Nobre and I believe there are already indications that the tipping point is close9 - and needs to be addressed right now with pro-active reforestation to build back the margin of safety. There have been historic droughts in 2005, 2010 and 2016/17 which can be considered the first flickerings of the tipping point. In the southern Brazilian Amazon the dry season is a month longer than historically. There has been a shift in forest composition in favor of lower rainfall tree species indicating the vegetation is already starting to shift.
While the hydrological cycle is important for the entire Amazon (and the continental climate system) what happens in Brazil is particularly critical. That is simply because the cycle starts in the east and carries moisture westward. The impacts of dieback will be most dramatic in southern and eastern Brazilian Amazonia.
Currently the entire Amazon forest is about 17% deforested whereas the Brazilian portion is 20% deforested. Of that latter about 23% is abandoned and in varying states of recovery10.
Deforestation had always been part of the Amazon situation but was relatively minor until the advent of major infrastructure projects which provided access to otherwise remote forest. The Belem-Brasilia highway led the way in the 1960s as part of a larger TransAmazon Highway system. There was major impact revealed first by satellite imagery in the 1980s around a fairly well designed but poorly executed project in Rondonia11.
A more worrisome plan, the Initiative for the Integration of the Regional Infrastructure of South America (IIRSA), was launched by the 12 South American countries in 2000. It included highway plans that would cut through the heart of the Amazon.
In the 1990s significant assistance began to be provided through the G-7 Pilot Program for the Brazilian Rainforests managed by the World Bank. The Brazilian government made environment a priority, including hosting the Earth Summit in Rio de Janeiro in 1992. Brazil has generally welcomed international assistance (e.g. the Amazon Fund provided by Norway and Germany and the two Amazon Region Protected Area (ARPA) which helped consolidate and management of the significant number of new protected areas and demarcated indigenous reserves).
From 2005 through 2012 concerted effort to reduce illegal deforestation was demonstrably successful although it did begin to rise toward the end of the worker party’s time in power (See Figure)12. With the election in 2018 of Jair Bolsonaro, there was considerable anti-environmental rhetoric and enforcement efforts were curbed and weakened. Deforestation not only rose but so did extensive use of fire. While fire has always been part of how Amazon farmers manage the land, especially after deforestation, it is not a normal part of Amazon ecology because standing forest is too wet to burn.
Source: IPAM, based on official data from PRODES/INPE.
In August 2019 the Brazilian public and then the world were awakened to the extent of the problem when so much smoke was blown into Sao Paulo that street lights were turned on early. That drew national and international attention to a dramatic increase in deforestation. There have been some efforts to address the fire issue but deforestation and fire in 2020 were greater than 201913.
It is hard to be precise about how much deforestation would cause the system to actually tip toward conversion to savannah. Carlos Nobre thinks 20-25%14. Tipping probably isn’t instantaneous which means it should be possible to work the system back from the brink. It clearly makes no sense to discover the tipping point by tipping it. The amount of abandoned deforested Brazilian Amazon may be providing a partial cushion and time for action. Much of that if encouraged to regrow as forest can provide the essential security (enough trees and leaves!) to keep the hydrological cycle healthy.
In the Central Amazon, where the forest fragments study is located, forest recovers pretty spontaneously but there are some indications recovery is harder in the southern Amazon probably because it is now drier15. Reforestation could stabilize the hydrological cycle and help Brazil fulfill its pledges under the Paris climate agreement. A modest portion could be agroforestry that provides additional economic return.
But what of all that biodiversity? Is it to be locked away for the amusement of science with no practical value? It has in fact contributed substantially to human wellbeing in ways that simply are not tracked or entered into human accounting. Commodities like cacao, quinine, and cassava (the major starch in the diet of most tropical peoples) all come from the Amazon. Curare which is used as a muscle relaxant in major abdominal surgery is still harvested directly out of the Amazon. Too complex to be synthesized without prohibitive expense, it was originally used (and still is) by indigenous peoples for fishing - relaxing the fishes’ muscles long enough for them to be harvested.
Yet more significant is the way the biodiversity can serve as a vast library for the life sciences. Each species constitutes a set of solutions to a particular set of biological challenges, any one of which can have a transformative effect on the life sciences and human wellbeing.
One of the most amazing examples involves the fer-de-lance (a poisonous viper of the new world tropics), the poison of which causes the blood pressure of whatever it bites to dive to zero. Studying this, scientists at Brazil’s Butantan Institute in Sao Paulo (which specializes in natural toxins and poisons) discovered an unrecognized system of regulation of blood pressure in mammals – now known as the angiotensin system.
Snake venom itself will not work as a medicine because it is denatured by the human digestive system. Instead scientists at the Squibb pharmaceutical company were able to design a molecule which works on the system. Known as captopril it was the first of the angiotensin converting enzyme (ACE) inhibitors. This class of drugs today benefits literally hundreds of millions of people by controlling their blood pressure and enabling longer healthier and more productive lives – an astonishing and ongoing impact.
The vast majority of the people who benefit from ACE inhibitors have little clue from whence it came. Even though the line of inquiry started in Brazil with the fer de lance, there was (and is) no direct way that some of the profit could enure to any Brazilian entity because 1) there was no molecule from Brazilian biodiversity which could be the basis for economic return, and 2) discovery of the angiotensin system was in the open scientific literature. Today with considerable development of biodiversity access and benefit sharing protocols there could be a better local benefit.
Nonetheless a more organized approach to exploring the biology of Amazon (or other) biodiversity could easily lead to sustainable economic benefits. Costa Rica had a successful initiative, INBio, which during its relatively short history explored ways in which these benefits can be systematically investigated and potentially brought to market.
Bringing new medicines to market is probably the hardest of all the things that might be pursued, simply because they require such rigorous testing but there are numerous other and easier possibilities. Retired Pfizer Research Laboratory Director George Milne believes that an ecological screen could distinctly increase the success rate in examining natural compounds. An interesting example would be to identify which trees leaf cutting ants do not defoliate to create mulch for their undergound fungus farms. That would narrow the search for possible new natural fungicides.
Carlos Nobre’s call16 for a forest biodiversity based economy for the Amazon includes very sophisticated activities such as the foregoing, but also could involve much simpler activities like aquaculture. That has gotten a bit of a start in Acre and in the Peruvian Amazon. There is no reason it cannot be brought to scale bringing Amazon fish like tambaqui or arapaima to global status like salmon or cod.
Another part of the solution could be sustainable Amazon cities that do not have a heavy impact on local resources or biodiversity. Manaus, for example, while in a sense a special case because it benefits from an economic free zone, has nonetheless largely developed an industry based on assembly plants using materials that are not extracted locally.
As Manaus’s economic productivity grows, deforestation in Amazonas declines because opportunity is in the city. Energy costs of transport of parts and then products is currently fossil fuel based but mostly by water transport which is more efficient than other means. Every city of course has a regional impact in terms of an agricultural footprint for the populace but again there are less impactful approaches than others.
A future Amazon that has not benefitted from a thoughtful biodiversity based development trajectory will be but a pale shadow of what the early explorers encountered. Dieback will lead to a hydrological cycle in tatters, stranded hydroelectric facilities, largely failed fisheries, marginal urban economies and impacts on continental climate.
The loss of moisture and its cooling effects in the Amazon basin itself will lead to serious increase in temperatures. In addition, if current trajectories of deforestation from poorly conceived infrastructure, from agricultural initiatives from cattle to oil palm and other biofuels (which will result in net loss of CO2 to the atmosphere) proceed unfettered, the Amazon will be transformed from an Eden into a highly degraded nightmare.