Tropical bird biodiversity and ecosystem services in fragmented landscapes

Transcription

1 Tropical bird biodiversity and ecosystem services in fragmented landscapes Sunshine Van Bael Smithsonian Tropical Research Institute Tulane University

2 Melting polar ice caps, sea-level rise NASA composite image

3 3 million years ago Polar ice caps were building and sea levels were dropping Mesoamerican land bridge was formed The great faunal interchange These events were key for high species diversity in this region

4 10,000 years ago Fifty thousand years ago, continents were populated with more than 150 genera of megafauna. By 10,000 years ago, at least 97 those genera were gone Barnovsky et al., 2004 VOL 306 SCIENCE Hunting

5 Today s Mesoamerican megafauna Domestication is easier than hunting!

6 Fragmented landscapes

7 Bird Migration National Geographic

8 Ecosystem roles of birds Pollination Predation of insects & other vertebrates Seed dispersal Seed predation Scavengers

9 Ecosystem services

10 Birds and humans types of ecosystem services Provisioning domestic fowl hunting Regulation Vectors of disease (avian flu) Control of disease (mosquito consumption, scavenging) Supporting Pollination, seed dispersal, pest control Cultural Avitourism; U.S., 45 million bird watchers, spent $32 billion in retail stores in one year, economic impact of $86 billion, supported 860,000 jobs (LaRouche 2001).

11 The link between biodiversity and ecosystem services is elusive Do we need lots of bird species to serve these roles? For example; Panama 968 bird species US & Canada 600 bird species Does fragmenting a landscape and decreasing bird species number matter?

12 Agua Salud Project Allows comparison through time of how bird community changes with respect to changing landscape context

13 Agua Salud baseline bird abundances Van Bael et al. 2013

14 Agua Salud baseline bird diversity Van Bael et al. 2013

15 Species composition is different- birds likely play very different roles Mature forest Reforestation New secondary Cattle Pasture Van Bael et al. 2013

16 Elusive link between biodiversity and ecosystem services Experimental evidence linking biodiversity to ecosystem services is rare. Previous experiments are small scale (mesocosm studies). Huge temperate bias for these types of experiments. Hypotheses for biodiversity roles in ecosystem function need further support

17 Hypotheses for biodiversity roles Diversity-productivity Greater diversity leads to greater overall biomass or productivity (supporting and provisioning service) Diversity-stability Greater diversity leads to greater overall ecosystem stability (regulating service) Sampling effects Greater diversity leads to a greater possibility of one trait to be present, and that trait influences ecosystem processes

18 Exclosure experiments: Do birds affect insect abundances and their damage to plants? no birds birds present

19 Exclosure experiments in Panama Birds limited herbivore abundance and damage in the canopy of a tropical forest Van Bael et al. PNAS 2003, Oecologia 2005 Bats also play a role in reducing insects and their damage to tropical trees Kalka et al. Science 2008 Birds limit herbivores on cacao trees Van Bael et al. J. Trop. Ecol. 2007, Van Bael et al. Biodiv.& Conserv 2007

20 Birds decreased insect abundance on cacao trees 22 No. arthropods/m 2 leaf area APR JUN OCT control, accessible trees exclosure, inaccessible trees Van Bael et al. 2007

21 Bird foraging on insects led to less leaf damage for cacao trees 13 Mean % Leaf Damage (SE) February April June October January control, accessible trees exclosure, nonaccessible trees Van Bael et al. 2007

22 Elsewhere in the Mesoamerican corridor AGROFORESTS VS. FORESTS Is there an overall effect of birds removing insects and reducing plant damage across many sites? Is this different in agroforests versus forests? WITHIN AGROFORESTS Can we expect greater ecosystem services from birds where their diversity is higher?

23 Data sources Forests = 30 (24 temperate, 6 tropical) Agroforests = 11 Moguel & Toledo 1999 Bird point counts (25m radius)

24 ln Response Ratio Birds reduced insects and their damage. The effects were similar in forests and agroforests. 0 All Arthropods Herbivores Carnivores Plant Damage Forest Agroforest Van Bael et al Ecology 2008

25 % arthropod reduction % arthropod reduction % arthropod reduction 100 More bird species correlate to greater levels of insect removal # bird species 0 *** *** # migrant species # resident species Suggests that migratory birds are driving this pattern Van Bael et al Ecology 2008

26 % arthropod reduction Why is this a key result? Shows that bird diversity influences the outcome of ecosystem services # migrant species Van Bael et al Ecology 2008

27 Biodiversity link to ecosystem services in agricultural systems Assigning a $ value is easier to do in agricultural systems. Two recent studies: Coffee in Costa Rica: Birds reduced coffeeberry-borer infestations by 50%; annually preventing losses of US$/hectare (Karp et al. 2013) Cacao in Indonesia: 31% yield reductions due to insect damage when birds & bats are excluded; 730US$/hectare (Maas et al. 2013)

28 How does landscape context influence biodiversity (and ecosystem services)? Bird community differences Bird behavioral differences

29 Landscape context matters for bird communities Reid et al. 2014, PLOSone

30 Patch size more important than vegetation structure Forest bird biodiversity depends on large contiguous patches Shape matters; compact is better than linear for preserving biodiversity Graham and Blake 2001

31 Types of corridors Riparian along rivers Landscape/Agrofores try Stepping Stone Living Fence

32 Bird behavior in fragmented landscapes Many tropical species do not cross open areas Have large area requirements Corridors may be influential in a bird s ability to disperse to another forest patch.

33 Corridors influence bird behavior Return success by antshrikes (gray bars) and wrens (black bars) in the three treatments following translocation. Gillies and St. Clair 2008

34 Two forest bird species Gillies and St. Clair 2008

35 Areas for future research in tropical landscapes Demonstration of links between biodiversity and ecosystem services Experiments to show how corridors influence biodiversity and related ecosystem services, at local and geographic scales Experiments to better understand how birds and other animals behave in fragmented landscapes

36 Thank you! Funding: Smithsonian Tropical Research Institute Smithsonian Migratory Bird Center Key Collaborators: Russell Greenberg Ruby Zambrano Peter Bichier Isis Ochoa Jefferson Hall