Creatures great and small

Published: September 18, 2010
The Australian

Eva Plaganyi-Lloyd

A few minutes outside Iquitos, in the Peruvian rainforest, we see our first river dolphins, their sharp fins slicing through the rich brown waters of the Amazon River.

The grey river dolphin Sotalia is one of five freshwater species, one of which, China's Yangtze river dolphin, was declared extinct just a few years ago, unable to mitigate the unrelenting effect of too many people trying to share its habitat.

The pressures of Iquitos, with about 30,000 inhabitants, are felt on the surrounding Amazon jungle, too.

Accessible only by air or a long river journey, this remote jungle city is a vibrant hub of activity and zigzagging motorcycles.

It is another three hours by small motorboat before we spot our first pink river dolphins (Inia geoffrensis). A loud splash and telltale wake alert us to a pod of rounded pink heads just breaking the surface.

This is among the most unique animals, restricted to the upper reaches of the Amazon basin.

My eyes strain to glimpse beneath the surface of their meandering world of river and submerged forest. But, unlike the dolphins, I am ill-equipped for the opaque river water.

It's no wonder these creatures have abandoned the need for eyesight and rely instead on sophisticated sonar to find their way and their prey.

I've watched oceanic dolphins across the world, and my mind races at the amazing circumstances that led to these dolphins colonising the biggest river system on earth.

The obvious explanation seems to be that long ago they swam 3000km upstream from the Atlantic Ocean. But the likelier scenario is even harder to contemplate: 10 million to 15 million years ago a great river on the South American continent flowed westward (the reverse of today) into the Pacific Ocean.

Movements of the earth's plates that eventually led to the rise of the Andes (which continue to rise) blocked the river's path to the sea, forming a vast lake.

Some of the trapped marine animals adapted and survived and, eventually, the elevation of the Andes, the source of the Amazon, led to the birth of the Amazon River, which today flows eastwards towards its mouth in Brazil.

This slow-moving body of water is constantly in flux, with seasonal changes in the water level from 10m to 20m. The surrounding land is divided into terra firma, or solid ground, and varzea, the flooded forests.

As the river rises each year, its animal inhabitants swim between submerged tree trunks while the human inhabitants remain dry in their houses on stilts.

This is the home of piranhas, caimans, the ancient hoatzin bird, poison dart frogs, anacondas and the richest biodiversity on the planet.

As I walk through the near-impenetrable marshy jungle it is not hard to imagine that this vast landscape may yet conceal unknown tribes and undiscovered ancient cities.

I can't imagine a more diverse country than Peru. Retracing my steps from the tropical Amazon jungle across the Andes and back down to the sea, a few days earlier I was in one of the driest deserts in the world.

In contrast to the barren desert soil, the offshore waters are highly productive. Fed by the nutrient-rich, cold Humboldt Current, Peru boasts the biggest fishery in the world, landing seven million tonnes of anchovy annually.

I am in Peru as part of a Lenfest forage fish taskforce to research management recommendations for fisheries such as this one, which contribute not only to the world's protein supply but are vital to support the diversity of fish, dolphins, birds and seals that rely on the same fish stocks for their continued existence.

Where once an estimated 10 million to 20 million seabirds populated the islands offshore from Peru, today there remain only two million. With time, these seabird populations resulted in accumulations of guano 40m to 50m high that in turn served as nesting habitats for penguins, boobies and other seabirds.

The guano industry sustained Peru's economy for about a century (being sold as fertiliser), but as the islands were scraped bare and the bird numbers started to fall, the value of the natural biodiversity was finally appreciated.

To Peru's credit, several mitigating actions were initiated, including establishment of the Paracas marine reserve, construction of walls on the guano islands and increased protection of marine species. But, as with elsewhere in the world, the question remains as to how much fish humans can take before they seriously affect the rest of the ecosystem.

Clearly there needs to be a fair balance; humans too depend on fisheries and this is all too evident in Peru where artisanal fishermen can be seen selling their catches at busy markets in desert areas where there is little protein to be had from the land.

But more than 90 per cent of the anchovy caught is ground into fish meal and exported for uses such as aquaculture. No wonder dedicated Peruvian scientists are working hard alongside some of the best chefs in the country to market fresh anchovy; their growing success thus far is commendable when considering the fine national cuisine that Peruvians are so proud of.

Gastronomic pleasures can range from fresh raw scallops in Paracas or a Lima restaurant offering the best seafood I've tasted, to sampling more than 100 varieties of potato, some of which are grown at altitudes near Cuzco that leave visitors scarcely able to breathe.

It's impossible not to marvel at the history of this ancient country at every step: home to the Incas, Machu Picchu, Nazca, strange pyramids, hidden cities.

On our boat trip out to the uninhabited Ballestas Islands archipelago, we pass the striking Candelabra carved on a hillside as we follow boobies and gannets to their roosts. Wing to wing the small islands are packed with jostling and squawking seabirds, while a few lazy sea lions drape the surrounding rocks.

It's been a good year so far for these animals, which suffer heavy mortalities in El Nino years when the cold upwelling currents are disrupted and the tap is turned on their fish lifeblood.

Because the animals have adapted to decade-long scale fluctuations in the productivity of their environment, it's critical to ensure that overfishing doesn't severely reduce their ability to survive periods of low food availability, especially given the uncertain effects of a changing climate.

After a solid day of rain, we are finally out exploring the Amazon jungle again.

Sloshing through knee-deep channels in our wellies, our guide Alfredo leads us to a small clearing in the Tahuayo communal reserve. Here we are rewarded by a bird show of 10 of the most vividly coloured species imaginable, including a paradise tanager and wire-tailed manikin.

We are transfixed until a mob of angry ants scales our boots and starts biting into our flesh.

The day before I had the misfortune of being stung by a scorpion; clearly this is no place for the fainthearted. But the rewards are extreme: a chattering party of titi and tamarind monkeys racing through the bushes alongside our canoe, a large sloth heaving itself and its baby along a branch and a rare glimpse of a river otter swimming to the bank.

Peru is an extraordinary destination and we all have a responsibility to ensure that the rich natural diversity of such wilderness areas are conserved for generations to come.

Eva Plaganyi-Lloyd is a scientist at CSIRO Australia and is a member of the Lenfest Forage Fish Task Force.

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Link to article in The Australian