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Indicators in Practice

Apr 16, 2014

Wildlife Picture Index

The Wildlife Picture Index (WPI) is an innovative tool that combines photos from camera traps and relevant environmental data to understand how well efforts to protect biodiversity are functioning. It was designed to address the need for robust biodiversity monitoring indicators to fulfill the Convention on Biological Diversity’s goal to reduce the rate of biodiversity loss by 2020. Measuring progress towards this target requires the use of data and indicators; however, the effectiveness of many biodiversity indicators falls short due to methodological constraints. The WPI aims to fill a need in biodiversity measurement by utilizing data from camera trap deployments to monitor changes in populations of ground-dwelling, tropical medium and large mammals and birds. This approach presents an easily standardized, cost-effective, and easily replicable tool to study these species, and allows for unbiased indicator estimation, making it extremely useful for monitoring programs aimed at measuring progress towards biodiversity conservation targets.
Tambako the Jaguar / CC / Flickr

Case Study: Wildlife Picture Index (WPI) Analytics System

Scope: Latin America, Africa and South East Asia

First Released: 2010; Augmented in 2013

Intended Audience: Scientists, governments, civil society  

Potential Application: Biodiversity monitoring and trend analysis, at varied scales

Developers: the Zoological Society of London, HP, and Conservation International

Data Collection: The Missouri Botanical Garden, the Smithsonian Institute, and the Wildlife Conservation Society (collectively the Tropical Ecology, Assessment and Monitoring (TEAM) Network))


DescriptionLinking together tech companies like HP with scientists and non-government organizations, the Tropical Ecology and Assessment Monitoring (TEAM) Network implements the largest global camera trap network in tropical forests. It first adopted the Wildlife Picture Index (WPI) in 2010 as a way to synthesize and understand the effects of climate and land-use change on tropical terrestrial mammal and bird diversity. In 2013, it released the first global WPI assessment for tropical ground-dwelling mammals and birds.

Relative to other field sampling methods, camera traps minimize human error and can accrue valuable data on species where visibility is reduced and encounter rates are low, allowing for unbiased and comprehensive indicator estimation. The WPI is derived from 1,000 primary camera trap deployments from 16 sites across three main continental forest blocks (Latin America, Africa, and South East Asia). Camera trap deployments occur by following either a random or systematic placement, and are left to operate during a given period of time during which they capture time-stamped photographs of species that pass through their field of view.

The WPI assesses changes to forest diversity and biodiversity, which are defined as the geometric mean of the occupancies of species in the community relative to the baseline, as defined by the first year of sampling (i.e., abundance at time t divided by abundance at time 1).  A WPI above one indicates a proportional increase in diversity relative to the first year of data (baseline). Values below one indicate a decrease in diversity. The WPI can be aggregated and disaggregated to capture trends at local, regional, and global levels, as well as within functional groups of interest, taxonomic groups, species with different designated conservation statuses, or species facing particular threats.  Ahumada et al. (2013) applied the WPI methodology to Volcan Barva, Costa Rica. Their comparison of different metrics of community dynamics – aggregated by hunting pressure and functional group – are displayed in the graphs below. These results suggest that existing management practices to control hunting in the area may not be adequate, and are indicative of the value of the WPI in developing management-oriented indicators.

Modeled changes in mammal species richness in Volcan Barva, Costa Rica. (Source: Ahumada et al., 2013)

The WPI represents an innovative tool for biodiversity monitoring through its computationally-advanced approach to modeling species populations using primary camera trap data. These models provide effective tools for monitoring trends in wildlife diversity that previously could only be roughly estimated, filling critical knowledge gaps and helping organizations determine where to focus their efforts to help minimize biodiversity loss. Additionally, when compared to more traditional survey methods, camera trap surveys are 15 to 30 percent cheaper to implement in forests and savannahs respectively, along with being methodologically superior with regards to standardization and reduced human error.  


Ahumada, J. A., Silva, C. E., Gajapersad, K., Hallam, C., Hurtado, J., Martin, E., ... & Andelman, S. J. (2011). Community structure and diversity of tropical forest mammals: data from a global camera trap network. Philosophical Transactions of the Royal Society B: Biological Sciences366(1578), 2703-2711.