Conservation - Scientific Papers

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One of the best Scientific Papers on the subject,  supported by bibliographical references of the most expressive.

Megafauna and ecosystem function from the Pleistocene 

to the Anthropocene

Yadvinder Malhi, Christopher E. Doughty, Mauro Galetti, Felisa A. Smith, Jens-Christian Svenning, and John W. Terborgh

PNAS January 26, 2016 113 (4) 838-846; published ahead of print January 26, 2016 

Edited by Robert M. May, University of Oxford, Oxford, United Kingdom, and approved December 10, 2015
 (received for review October 6, 2015)

Abstract

Large herbivores and carnivores (the megafauna) have been in a state of decline and extinction since the Late Pleistocene, both on land and more recently in the oceans. Much has been written on the timing and causes of these declines, but only recently has scientific attention focused on the consequences of these declines for ecosystem function. Here, we review progress in our understanding of how megafauna affect ecosystem physical and trophic structure, species composition, biogeochemistry, and climate, drawing on special features of PNAS and Ecography that have been published as a result of an international workshop on this topic held in Oxford in 2014. Insights emerging from this work have consequences for our understanding of changes in biosphere function since the Late Pleistocene and of the functioning of contemporary ecosystems, as well as offering a rationale and framework for scientifically informed restoration of megafaunal function where possible and appropriate.

For hundreds of millions of years, an abundance of large animals, the megafauna, was a prominent feature of the land and oceans. However, in the last few tens of thousands of years—a blink of an eye on many evolutionary and biogeochemical timescales—something dramatic happened to Earth’s ecology; megafauna largely disappeared from vast areas, rendered either actually or functionally extinct (1, 2). Only in small parts of the world do megafauna exist at diversities anything close to their previous state, and, in many of these remaining regions, they are in a state of functional decline through population depletion and range contraction. In the oceans, a similar process has occurred over the last few hundred years: although there has been little absolute extinction, there has been a dramatic decline in the abundance of whales and large fish through overharvesting (3). Both on land and in oceans, declines continue today (4⇓⇓–7).

Homo sapiens evolved and dispersed in a world teeming with giant creatures. Our earliest art forms, such as the haunting and mesmerizing Late Pleistocene cave paintings of Lascaux and Altamira, show that megafauna had a profound impact on the psyche and spirituality of our ancestors. To humans past and modern, they indicate resources, danger, power, and charisma, but, beyond these impacts, such large animals have profound and distinct effects on the nature and functioning of the ecosystems they inhabit.

Martin (8) first posited a major human role in past megafaunal disappearances, and, since then, much has been written on their patterns and causes and the relative importance of human effects, climate change, and other factors (8⇓⇓⇓⇓⇓⇓–15). Only recently has work begun to address the environmental consequences of this dramatic transition from a megafaunal to a nonmegafaunal world on Earth’s ecology, as manifested through vegetation cover (16), plant–animal interactions (17), ecosystem structure (16, 18), trophic interactions (7), fire regimes (19), biogeochemical cycling (20), and climate (21, 22).

In this paper, we review evidence for megafaunal impacts on ecosystem function, on timescales ranging from the Late Pleistocene to the present. Understanding the consequences of past extinctions is valuable for a number of reasons: in particular because the loss of megafauna may have an enduring but little-recognized legacy on the functioning of the contemporary biosphere. Much of our current understanding of ecosystem ecology and biogeochemistry has been developed in a world artificially depleted of giants. We explore what lessons can be learned from the impacts of past extinctions and declines for contemporary conservation and explore what role megafauna may have yet to play in maintaining and rebuilding viable and vibrant ecosystems.

Continuation: http://www.pnas.org/content/113/4/838#ref-48

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