By Sydney
The entire article with photos can be found at
Peering at the river’s glass water, which reflected the rich green of the forest canopy standing tall from both sides, I noticed a slight ripple followed by the splash of Amazonia’s beloved and famed pink river dolphin. It was unmistakable—large and uniquely pink in color with the fleeting appearance of its long snout and fins. This was my first dolphin sighting in Pacaya-Samiria National Reserve, but would certainly not be my last.
Much of my time in Amazonia has been spent in lowland secondary forest, where recent human disturbances have potentially impacted wildlife populations and I am thrilled to catch a glimpse of a monkey. At Pacaya-Samiria, it was impossible to miss the troop of 20 or more squirrel monkeys climb across the vines that hang into the river as the bellowing roar of howler monkeys echoed from deep within the jungle.
Peru was the first nation to establish protected areas in Amazonia. This began with the creation of the Pacaya Reserve in 1940 and the Samiria Reserve in 1954. Now referred to as Pacaya-Samiria National Reserve, this extremely seasonal and high-nutrient flooded forest is located in the Marañon-Ucayali subsidence area. It covers an area of 20, 800 km, about the size of Israel.
For three days, I lived with other students on a boat parked within this reserve. This is where I learned of the various threats to flooded forest wildlife populations as well as the importance of long-term wildlife monitoring and of setting aside protected areas for these animals to thrive in their natural habitats.
The question of climate change in flooded forests of Amazonia
Like the stock market, flooded forests experience a boom and bust cycle in water levels. Research in Pacaya-Samiria reveals the potential impact of climate change on variability of dry and wet seasons in the flooded forest.
An article published in Conservation Biology journal details a study conducted by Dr. Richard Bodmer, of Durrell Institute of Conservation and Ecology, and his team within the reserve. According to the article, climate change intensifies water cycles, increasing intensity and duration of flooding during wet seasons and creating low-water levels and less precipitation in dry seasons. These fluctuations shift wildlife populations, which are largely influenced by flooding and droughts.
The article described the five consecutive years of above normal flooding in the Peruvian Amazon from 2011 to 2015 during the high-water seasons, preceded by one year of intense drought in 2010. This was the longest period of high flood pulses since 1973 to 1977. Water level was significantly higher, with very few dry patches of levee forest remaining in Samiria River basin. Levees are long stretches of slightly raised land formed by changes in river channels.
These years were defined by the research team as historic flood levels. The team surveyed wildlife to estimate the effect of these intensive floods on aquatic, terrestrial and arboreal communities by gathering population densities.
Results indicated a severe crash in terrestrial mammal populations, which decreased by over 95 percent during the years coinciding with high water levels. In 2015, no terrestrial mammals were sighted. Terrestrial animals in this region include white-lipped peccary, red-brocket deer, agouti, anteater, armadillo and capybara. When water levels increase, these animals swim to dry levee forests to take refuge. High flooded years force terrestrial mammals onto smaller areas, increasing competition and predation. The historic flooding levels saw drowning in terrestrial mammals.
The lowland tapir, the largest terrestrial animal in the Amazon, was the only member of the terrestrial group not affected. According to Bodmer, this is can be attributed to their abilities to swim and breathe while under water with their snorkel-like prehensile trunks.
Arboreal species include squirrels, sloths, primates, birds, bats, among others that live in trees. Overall, this group remained stable during the high floods. The primates who are most successful in flooded forests are those that can alter their diet, because during floods, fruits drop from the canopy into the river to disperse seeds. Woolly monkeys eat leaves during floods and tamarin monkeys drill holes in trees to eat insects, while spider monkey populations are low in flooded forests because they eat fruits year-round. Wildlife that can climb trees or have arboreal habits escaped the effects of floods. However, arboreal species could experience populations changes resulting from decreased seed dispersal of mammals, which could alter forest structure and food resource availability.
Aquatic species, including fish, dolphin, caiman, and otters, also remained stable during these high floods. Pacaya-Samiria, as the largest flooded forest in the area, has a large fish population. According to the Bodmer article, during high-water seasons fish enter the flooded forest to access the abundant resources. The fallen fruits in flooded forest rivers become food sources for fish stocks, which explains their increase up until 2015. The intensive flooding extended their breeding seasons, increasing their stocks. In the dry season, water recedes and large numbers of fish migrate form the Samiria River basin into the larger Marañón River where groups of birds and dolphins feed on the fish.
The Cocama indigenous people of Pacaya-Samiria have taken measures to adapt to these multi-year climatic cycles and how this alters the availability of fish and wild meat sources. In response to shifts in wildlife populations resulting from these high floods, Cocama people increased fishing and decreased hunting. The increased fish stocks during flooding compensated for decreases in wild meat.
“Cocama are very adaptable. They have to be,” Bodmer said in a lecture. “This adaptive strategy to climate change is surely not new.”
The increased variability which resulted in the five years of intensive flooding is potentially climate-induced, according to the article. However, Bodmer stressed that this theory has limitations, especially in foreseeing the consequences climate change poses on our future.
“What we know is the current situation. We can’t predict the future very well,” he said.
However, the article does paint a picture of the future based on this phenomenon. The worst conditions, both for wildlife and the local people, would be in the years of consecutive floods followed by consecutive droughts. The flooding would diminish terrestrial populations, and fish mortality during the drought would occur quicker than the recovery of wild meat species. This would threaten food security and possibly heighten unsustainable hunting and fishing.
Climate change could therefore lead to the unraveling of a series of events that would further exacerbate environmental damage. The article presented the need for maintenance of habitats and wildlife population, prevention of overuse and deforestation, and the sustainable use of food resources.
“Conservation scientists need to know how physical changes result in biological changes in wildlife and how these cause change in resource use, sustainability and management of local people in Loreto region of Peruvian Amazon,” the article stated.
Protecting the plethora of life
Climate is not the single perpetrator of biodiversity loss. In Amazonia, biodiversity is threatened by pollution—including the contamination of water due to oil drilling; land use changes—including the building of dams and urbanization; and overexploitation of resources—including overgrazing, logging, overhunting, overfishing, and many exploitative activities that contribute to deforestation.
These practices are mitigated by the successful establishment of co-managed protected areas—spaces such as Pacaya-Samiria National Reserve that integrate local people in reserve management. Certain activities are still permitted in the reserve, such as sustainable resource use and traditional activities of subsistence fishing and hunting.
Bodmer works with Earthwatch volunteer groups to monitor wildlife populations in Pacaya-Samiria. He has worked in the reserve for over 20 years and promotes co-management of the land between natives and government agencies. Bodmer has written about the economic importance of bushmeat hunting to rural poor Amazonians.
“If well managed, bushmeat hunting can provide long-term socioeconomic benefits to local communities and help conserve Amazonian biodiversity through maintaining intact rainforests,” he wrote in a chapter of Wildlife and Society: The Science of Human Dimensions. “If poorly managed, bushmeat hunting will lead to the extirpation of animal populations, reduced socioeconomic benefits that rural people obtain from wildlife, and a decreased value of intact forests.”
Throughout the duration of my time in the reserve, I contributed to this long-term wildlife monitoring data collection. Surveys of wildlife were divided into those monitoring resource-use species—those used by people such as fish, caiman and tapir; and indicator species—those not used directly by humans such as dolphin and macaws.
Healthy abundance of these species indicates a healthy ecosystem.
We conducted surveys both on boat and in the forest. For a set distance or time, we recorded the number of animals detected as well as their behavior, size and other additional information. We monitored dolphin, fishing bats, wading birds, macaws, fish, terrestrial mammals, and caiman. Wildlife abundance can be compared between these standardized surveys throughout time to estimate if there are declines or upsurges in animal populations.
Dolphins, including pink and grey, are considered indicators of the aquatic system. This species is highly valued by local people and are therefore not threatened by hunting.
However, they will move out of the area with significant changes to the ecosystem. A species considered rare to view, pink river dolphins bounded from the water in groups as commonly it seemed as birds flew overhead.
Fishing bats, which we monitored at night, are indicators of the small fish. In swarms, these bats flew just above the surface of the water, at any moment ready to dip down to catch their fish prey. Bodmer said wading bird populations are more reliable indicators of fish populations than the fish themselves because these are their food sources. I observed kingfishers, egrets, horn-screamers, herons, the Amazon tern, a hoatzin, among many others.
Macaws are fruit-eaters and are therefore indicators of the forest system. If fruit is scarce, they move from the region. The blue-and-yellow macaw is common in flooded forests and at Pacaya-Samiria they soared in flocks above the forest canopy calling to each other in raspy intonations. Parrots were largely traded as pets in the 1970s through the 1980s. Many countries have placed restrictions on the trade or prohibited it entirely. However, Bodmer said captive breeding in the pet trade has increased in the United States.
Until coming to Amazonia, my best knowledge of parrots came from interacting with pet macaws. Observing these animals in the wild, flying freely within their large natural habitat, illustrated the extent to which the pet trade restrains the natural habits of these birds and the significance of protecting them from the cage.
We monitored fish population by using net and line to catch the fish for an hour. We weighed and measured them before returning them to the river. My group recorded data for 79 fish, including piranhas, sardines and armored catfish.
During terrestrial transects, I observed monk saki monkeys, white capuchin monkeys and woolly monkeys. I also watched a troop of howler monkeys leap from one tree to the next. A truly unique experience was watching one of the larger members of this group form a bridge between the two trees, allowing a smaller howler to walk across its back.
Apart from the animals monitored, I saw squirrel monkeys, river otters, capybara, toucans, turtles, and a sloth hanging from a tree. This is an impressive list considering my little experience in wildlife detection and my limited time at the reserve. Within Pacaya-Samiria, even the untrained eye will have an easy time viewing the plethora of wildlife and will come to appreciate the value of observing species in the wild.
Protecting the jungle’s apex predators
Caiman are crocodilians similar to the alligator but with an armored belly and native to tropical America. Caiman populations found in Pacaya-Samiria include the black caiman—the jungle’s apex predator that can reach up to five meters long, the smooth fronted or dwarf caiman—among the smallest caiman in size, and the spectacled caiman—almost the size of the black caiman.
Caiman are nocturnal and therefore we surveyed them by boat along the river at night using spotlights to detect caiman eyeshine. Once their presence was indicated, additional observations such as size and species were gathered if possible.
The spectacled caiman population demonstrated a long-term decrease, according to the Bodmer article, before the intensification of river levels. They continued to decrease during years of consecutive flooding, while black caiman had stable populations during these years.
In the 1960s to mid-70s, black caimans were exploited for their leather pelts which caused major deterioration to their population. A large quantity of these were exported to the United States. CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, is an international agreement between governments which seeks to guarantee that international trade in wild animal and plant specimens does not threaten their survival. Under CITES, caiman fall into the category of species that cannot be traded internationally, as animals or products, unless for scientific purposes.
Despite a population renewal, caiman is still used by Amazonian people in Loreto, Peru.
Bodmer said this use results in lower numbers of caiman in the Loreto rivers compared to the relatively healthy populations found in the protected Pacaya-Samiria. Bodmer said a household interview found that one to two caimans are consumed each year.
Censuses of black caiman in Pacaya-Samiria in 1995 when the reserve administration implemented strict control over local people, and in 2005 when park management began to involve local communities in co-management, revealed an increase in black caiman populations within the reserve. This coincided with reduced hunting levels.
“Many local people changed their attitude toward the reserve and began to see long-term benefits of the reserve,” Bodmer wrote in Wildlife and Society. “The reserve became part of their future plans, and there was increasing interest in getting involved.”
While caiman populations are protected and maintained in Pacaya-Samiria, elsewhere in Loreto I have only witnessed caiman as commercial products for consumption in Belen Market. Caiman are an example that underscores the contrast in wildlife populations between protected and unprotected areas.
Pacaya-Samiria exemplified the potential for a forest ecosystem to flourish once protected from unsustainable and non-managed practices. It exemplified the importance of long-term data monitoring both to detect shifts in wildlife populations and to use that information as an indication of the ecosystem’s overall health. In the wake of climate change, it is vital to be prepared for the future by being armed with as much information as possible.
“We want to be able to deal with climate change and make decisions for moving forward,” Bodmer said.
As someone who has witnessed both unprotected and protected Amazonian jungle, I can attest to the higher wildlife population levels in the reserve. This can be seen simply with the human eye; no data collection is needed for my conclusion. However, not everyone is lucky enough to have observed and compared different regions of Amazonia. Wildlife monitoring is essential to convey this information. It’s use is necessary to influence policy and justify setting aside this space for the preservation of wildlife within a healthy forest for generations to come.


About the author:

My name is Sydney Amodio. I am currently living and researching in the Amazon jungle in Peru.

I was attracted to the Amazon because of its unique biodiversity and culture. I hope to learn about what myself and others can do to conserve this ecosystem and protect it from internal and external environmental threats.

Follow along on my adventures and research as I post updates, photographs and videos of my 100 days in the Amazon.