Study results, published in the Journal Philosophical Transactions of the Royal Society B: Biological Sciences show that the understanding of animals and their physical traits is vital to saving tropical ecosystems.

According to the research, understanding land-use change is important because tropical forests are integral to the long-term stability of global air quality and climate cycles. The health of tropical forests is reliant on biodiversity - and is helped by animals spreading seeds to regenerate growth. In fact it is thought 90% of tropical tree and shrub species rely on animals for seed dispersal.

Lead author of the study Dr Tom Bregman of Oxford University and the Global Canopy Programme, says: "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."

Scientists worked across 330 locations in different habitat types varying from soybean fields to undisturbed forest with a team of scientists looking at potential change on two ecosystem processes for which birds play important roles, specifically with regard to seed dispersal and insect predation.

According to Dr Alexander Lees, one of the scientists involved in the research from Manchester Metropolitan University, the study is extremely timely: "Understanding the implications of the loss of bird species for ecosystem function is crucial to our understanding of the future trajectories of Amazonian landscapes, he said.

Data on bird community composition, collected by the Sustainable Amazon Network, was reviwed together with 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. Data from bird specimens deposited in museums in Brazil, the UK and the USA was also used.

The team recorded 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.

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. For example, the loss of large-billed and long-winged species in agricultural landscapes and in regenerating secondary forests means that certain large-seeded tree species will likely not have their seeds dispersed in future.

The loss of certain kinds of insectivorous bird species will also 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.

Dr Joseph Tobias, of Imperial College London, says: "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." He added that these services collapse in agricultural land-uses such as pasture and arable.

Dr Lees adds: "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.

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Laura Briggs is the Ecologist's UK news reporter specialising in reporting on ecology and the environment. You can follow her here @WordsbyBriggs