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Ama­zon rain­for­est metrop­o­lis casts 1,000 km shadow on wildlife

pub­lished 06 August 2017 | mod­i­fied 06 August 2017

Tambaqui fishUrban food demand in the Ama­zon could be hit­ting wildlife up to 1,000 km away from the city, accord­ing to new research.

Rapid urban­iza­tion in the Brazil­ian Ama­zon means over 18 mil­lion peo­ple are now liv­ing in rain­for­est towns and cities but the impact of this demo­graphic change on wildlife har­vested for food, is largely unknown.

In an attempt to find out more, researchers from Lan­caster Uni­ver­sity went into rural com­mu­ni­ties in remote trop­i­cal wilder­nesses along the Purus River, a major Ama­zon­ian trib­u­tary, over a period of a year to gather evidence.

Amazon Purus riverBoat­ing down the River Purus as part of field­work.
Image credit: Dr. Daniel Tregidgo Lan­caster University.

Using tam­baqui, a fish species highly prized by Ama­zon­ian con­sumers, as an exam­ple, they inter­viewed hun­dreds of rural Ama­zo­ni­ans about their fish­ing activ­ity along a heav­ily fished but oth­er­wise rel­a­tively pris­tine river which flows towards Man­aus — a city of over 2 mil­lion res­i­dents. All fish­ers were asked in detail about the catch, effort and catch meth­ods of every fish­ing trip that they had under­taken in the three days prior to the interview.

The results were pub­lished online on 24 July in the jour­nal PNAS, and the data revealed that the tam­baqui fish became much smaller and harder to catch nearer to the rain­for­est metrop­o­lis. Ama­zon­ian fish­ers reported a 50% reduc­tion in body size and catch rate as the river approached the city. Sur­pris­ingly, the research team found this trend extended as far as 1000 km from the city, where larger fish were more com­mon and eas­ier to catch.

This research has revealed for the first time exactly how far the defau­na­tion shadow of a metrop­o­lis extends into the ‘forested wilderness’.

Dr Daniel Tregidgo, lead author, Lan­caster Envi­ron­ment Cen­tre, Lan­caster Uni­ver­sity, United Kingdom

Researchers found these declines were linked to city-​based boats that pro­vide rural fish­ers with reli­able access to fish-​buyers and ice, fuelling overfishing.

The find­ings have impor­tant impli­ca­tions for wider for­est diver­sity and human liveli­hoods, which may suf­fer as a result of urban-​related species deple­tion or ‘defaunation’.

Dr Daniel Tregidgo said: “Our research shows the impact of urban demand for a high-​value species of river fish is felt much fur­ther away from cities than we imag­ined. This is sig­nif­i­cant because the trop­ics har­bour two-​thirds of the Earth’s bio­di­ver­sity and are expe­ri­enc­ing rapid human pop­u­la­tion increase, urban­iza­tion and eco­nomic change result­ing in higher urban food demand.

Much of this demand is being met by the expan­sion of farmed meat pro­duc­tion but wild meat such as fish and for­est wildlife is also an impor­tant food for hun­dreds of mil­lions of trop­i­cal con­sumers, from the poor­est and most vul­ner­a­ble to wealth­ier urban res­i­dents. This research has revealed for the first time exactly how far the defau­na­tion shadow of a metrop­o­lis extends into the ‘forested wilderness’.”

(Source: Lan­caster Uni­ver­sity news release, 25.07.2017)

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