Ecologists learn lessons from the ‘ghosts of megafauna’


Scientists have been assessing the ecological consequences of a megafauna-depleted world and what, if anything, should be done about it.

Researchers discussed whether the loss of big beasts contributed to regional and global system changes, such as Arctic warming and more wildfires.

Megafauna (animals with a mass of 44kg or more) once dominated but disappeared in an ecological "blink of an eye".

The global scientific gathering was held at the University of Oxford, UK.

Co-organiser Yadvinder Malhi, professor of ecosystem science at the university's Environmental Change Institute, said the conference was "unique" as it brought together many disciplines that would not normally meet during their day-to-day work.

'Huge impacts'

Assessing the event's discussions, he observed: "There was such a strong consensus emerging that megafaunal extinctions did have a huge impact on the structure of ecosystems, which still ramifies through to the ecosystems today.

"What we think as natural now are still carrying many disequilibria – or ghosts – resulting from the loss of the megafauna in terms of their structure, functioning and nutrient recycling."

Prof Malhi added that a greater understanding of the impacts of megafaunal extinctions helped researchers model the consequences of losing big beasts from today's landscapes in sub-Saharan Africa and Asia.

"Somehow, it seems as if megafauna have been linked to dinosaurs in people's popular imagination," he told BBC News.

"But, ecologically speaking, it was only a blink of an eye ago that there were megafauna everywhere."

Written By: Mark Kinver
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  1. @OP – Researchers discussed whether the loss of big beasts contributed to regional and global system changes, such as Arctic warming and more wildfires.

    The evidence indicates that megafauna can be key determining factors in whole ecosystems.

    The role of elephants in forests and savannahs is a modern example.

    As the largest frugivores on Earth, elephants have unique ecological properties. Found in deserts,
    savannahs, and forests, they are the last remnants of a diverse lineage. Among the three currently
    recognized forms, African forest elephants are the most frugivorous, followed by Asian and African
    savannah elephants, although their role as seed dispersers is variable and context-dependent. African
    forest elephants may consume more seeds from more species than any other taxon of large vertebrate
    dispersers, defecating them over long distances in viable conditions into nutrient-rich and protective
    dung.** In short, elephants are forest gardeners. The signature of elephant dispersal is evident in the spatial
    distribution of trees suggesting that elephants maintain tree diversity and retain low redundancy in
    seed dispersal systems. Large numbers of forest elephants ranging over large areas may be essential for
    ecosystem function**. The loss of elephants will have important negative consequences for the ecological
    trajectories of some plant species and whole ecological communities, yet the conservation status of forest
    elephants is catastrophic in Asia and rapidly becoming so in Africa due to hunting and other conflicts
    with people. In this paper we review the current knowledge of elephants as seed dispersers, discuss the
    ecological consequences of their decline, and suggest priority areas for research and conservation action.

    Forest elephants not only widely distribute tree seeds in their dung maintaining diversity in forests, but other elephants push over trees to feed from high branches during droughts, thus keeping the grasslands open rather than being swallowed by encroaching jungle.

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