Plain Language Summary: Linking the biodiversity impacts and monetary costs of alien birds.

By Thomas Evans, Elena Angulo, Christophe Diagne, Sabrina Kumschick, Çağan Şekercioğlu, Anna Turbelin and Franck Courchamp.

Read the full paper here.

A species is considered to be alien when it has been introduced by humans to places where it would not normally live. Some alien species have damaging impacts on nature (e.g., by spreading diseases to wildlife) and people (e.g., by consuming agricultural crops which affects livelihoods). We wanted to find out whether alien bird species with the most damaging impacts on nature also had the most damaging impacts on people, as measured by their monetary costs (these costs result from damage to assets of human value caused by alien birds, and actions carried out to manage their impacts). We also wanted to find out whether alien bird species with specific types of impacts on nature (e.g., those that compete with native species for resources) also had high costs. This would be useful to know, as it would inform actions to manage alien species with damaging impacts on both nature and people.

We found alien birds that prey on native species (those that attack and kill wildlife) to be associated with high costs. This may be because predation can severely damage nature (e.g., by causing extinctions of wild animals) and is therefore managed to protect nature (and management actions incur costs). However, it may be because predation is easier to identify and occurs more frequently than other types of impacts on nature (e.g., hybridisation between native and alien species) and it is therefore more frequently managed.

We found alien bird species that occupy many different habitats and eat many different types of food (generalist species) to be associated with more severe impacts on nature and high costs. This may be because these species have many opportunities to cause impacts as they are likely to interact with, and affect, a wide range of native wildlife and to damage a wide range of assets of human value. Our study indicates that management actions that prevent the introduction of both predatory and generalist bird species to places where they would not normally live, or that reduce the spread of predatory and generalist alien bird populations, may have significant benefits for both nature and people.