School of Life Sciences

A harpy eagle in its nest in the Amazon Forest.

Research on World’s Largest Eagle’s Habitat Loss Came Out Top in 2021

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Research by Dr Everton Miranda, PhD graduate from UKZN’s School of Life Sciences, made waves in 2021 for revealing the urgent need for forest conservation to preserve precious resources necessary to sustain the world’s largest eagle, the harpy eagle (Harpia harpyja) in South America’s Amazon, and is among the top 100 ecology papers of the almost 2 000 published in Nature’s Scientific Reports journal last year.

Miranda, a lecturer at Mato Grosso’s State University in Brazil, graduated with his PhD from UKZN in May 2021 after conducting research through the Centre for Functional Biodiversity on building a conservation strategy for the harpy eagle in the Amazon Forest.

Miranda was supervised by Professor Colleen Downs, South African Research (SARChI) Chair in Ecosystem Health and Biodiversity in KwaZulu-Natal and the Eastern Cape as well as Professor Carlos Peres of the University of East Anglia in England. Their research in Scientific Reports investigated factors that could lead to the extinction of the Amazon’s apex avian predator.

Titled: Tropical deforestation induces thresholds of reproductive viability and habitat suitability in Earth’s largest eagles, this research was the first of its kind to examine the impact of forest loss on the birds’ feeding ecology. Scarcity of prey often drives local extinction of predators, meaning that if the eagles’ ability to acquire prey is not protected, they are at risk of dying out.

After identifying prey bone fragments and using cameras to monitor 16 active harpy eagle nests in landscapes in Mato Grosso that had experienced up to 85% forest loss according to maps and satellite imagery, Miranda’s research revealed that under current rates of deforestation, the Amazonian “Arc of Deforestation” will not be able to support breeding populations of the important birds.

Breeding pairs have already seen a decline of more than 3 000 since the mid-1980s, and with a low reproductive rate, the future of this species is under threat.

Publicised on global platforms, including BBC News, the study found that the large-taloned eagles relied on vertebrates such as monkeys, sloths and birds which live in forest canopies as food sources. Once the canopy habitat was gone and the prey with it, the eagles could not switch to open-habitat prey in deforested areas. In places where 50% or more of the landscape was deforested, the birds simply could not access enough food.

In those areas, harpy eaglets were starving to death in their nests or could not be reared to a stage of independence to hunt for themselves, and areas where deforestation affected 70% or more of the landscape did not support nests and reproduction at all.

In the area under study, only around 65% of forest cover remains after intensive deforestation activity over the past three decades, a concerning figure as rates of deforestation have not abated.

If the harpy eagle is to be protected, researchers say an absolute minimum of 50% forest cover is needed in the Amazon. When scaling up results, they estimated that more than a third of the 428 800km2 “Arc of Deforestation” that comprised their study region would not be able to support these birds.

Miranda stated that the eagles’ slow life cycle meant that their chances of adapting were close to zero, and that maintaining forest connectivity, translocating juveniles and supplementing the diet of eaglets were essential to help the birds persist in anthropogenically altered landscapes.

Despite perceptions that the eagles threaten humans or their livestock, resulting in some persecution and killings detailed in other research by Miranda, there is little evidence that harpy eagles do take advantage of livestock availability in deforested areas, and this persecution complicates their protection further.

Decisive forest conservation action, urges the research, is urgently needed to protect harpy eagles, whose population is concentrated in the Amazon rainforest and whose geographic range has shrunk by 40% since the 19th century.

Words: Christine Cuénod

Photograph: Supplied