Birds can help ecosystems bounce back from deforestation
Attempts to combat the impact of deforestation may fail unless we understand the physical traits of animals and how these matter for tropical ecosystems, according to new research.
To analyse the impact of land-use change on tropical forests – such as logging or conversion to agriculture – scientists need to look at data on species traits and show how these relate to ecosystem services.
A new study has found that a loss of birds cuts the chance of forests bouncing back from deforestation. It is the birds’ physical traits, such as beak or tail size, which provide a window for scientists to assess the impact of environmental change.
Understanding land-use change is important because tropical forests are integral to the long-term stability of global air quality and climate cycles. Tropical forests’ health is underpinned by biodiversity, with animals spreading seeds to regenerate growth.
Seed dispersal
Results published in the Journal Philosophical Transactions of the Royal Society B: Biological Sciences used data on bird community composition collected by the Sustainable Amazon Network and data on bird morphology from museum specimens to look at the ‘functional trait structure’ of Amazonian forest bird communities – size, diet, wing and tails, and their occurrence across habitats.
The team of scientists looked at potential change on two ecosystem processes for which birds play important roles: seed dispersal and insect predation.
Changes in supply of these ‘biodiversity services’ were assessed across 330 locations in different habitat types varying from soybean fields to undisturbed forest in the state of Pará in the Brazilian Amazon.
Dr Alexander Lees, from Manchester Metropolitan University, said that the study is extremely timely.
Recovery
He added: “Understanding the implications of the loss of bird species for ecosystem function is crucial to our understanding of the future trajectories of Amazonian landscapes.”
The results suggest that local extinctions of birds caused by the loss and degradation of their tropical forest habitats are not random with respect to the bird’s traits, that includes beak size and wing length.
The loss of large-billed and long-winged species in agricultural landscapes and regenerating secondary forests means that certain large-seeded tree species will likely not have their seeds dispersed in future. Likewise, the loss of certain kinds of insectivorous bird species will mean a lack of control of herbivorous insects, many of which can be pests in agricultural landscapes. The distribution of the species and their traits can then be used to assess whether we maintain or lose ecosystem functionality as land-use change intensifies.
Lead author Dr Tom Bregman, of Oxford University and the Global Canopy Programme, said: “We provide compelling evidence that the loss of tropical bird species following land use change will disrupt both seed dispersal and rates of insect herbivory, both regulated by birds. This has important implications for the ability of tropical forests to recover from human activities including deforestation.”
Museum specimens
Dr Joseph Tobias, of Imperial College London, added: “The ‘biodiversity services’ that tropical forest birds supply are crucial for forests to function properly. Our work shows that they are more effectively retained in primary forests that have not been completely cleared, rather than secondary forests regenerating after total clearance.”
Dr Tobias said that these services collapse in agricultural land-uses such as pasture and arable.
The scientists made good use of data from bird specimens deposited in museums in Brazil, the UK and the USA.
Dr Lees said: “Data from specimens held in natural history museums underpinned this study; yet these institutions are often woefully underfunded and undervalued, despite being crucial for efforts to catalogue and understand global biodiversity.”
Understanding the provisioning of key ecosystem processes such as seed dispersal and control of herbivory will help to understand whether tropical forests will have impaired or reduced resilience in future.
If this is the case, forests damaged by fire and logging are unlikely to come back strongly because species have been lost that assist in the process. Eliminating wild fires, reducing the impact of logging and enforcing the protection of hunted species will help to maintain the health of these ecosystem processes and the forests that depend on them.
ENDS
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NOTES FOR EDITORS
Paper: Using avian functional traits to assess the impact of land-cover change on ecosystem processes linked to resilience in tropical forests. Proc. R. Soc. B 20161289. http://dx.doi.org/10.1098/rspb.2016.1289
For more information, to speak to Dr Alexander Lees or for a copy for the paper, please contact:
Chris Morris, Press Officer, Manchester Metropolitan University. Email: c.morris@mmu.ac.uk or Tel: 0161 247 2184.