The Biodiversity Intactness Index (BII) measures the average abundance of originally present species relative to their abundance in undisturbed ecosystems. A BII of 1.0 represents a pristine ecosystem; the scientifically proposed safe operating boundary is 0.90 or above. The global average now stands at 0.73 — well below the safety threshold and declining.
Understanding the Index
The BII is constructed from ecological surveys spanning over 50,000 sites worldwide. It captures both species richness (how many different species are present) and abundance (how many individuals of each species exist). The index therefore reflects not just extinction risk but the broader degradation of ecological communities.
Regional variation is extreme. Tropical forests in Southeast Asia and West Africa have BII values below 0.55, while boreal forests in Canada and Russia remain above 0.85. Urban and intensive agricultural areas routinely score below 0.30.
Implications for Nature-Based Tourism
Tourism destinations that depend on wildlife encounters and pristine ecosystems face direct economic consequences from BII decline. Research correlating BII trends with tourism revenue across 34 national parks found that parks experiencing BII declines of more than 0.05 over a decade saw average visitor numbers decrease by 12% and average willingness-to-pay decline by 18%.
The mechanism is straightforward: visitors expect to see wildlife. As species abundance declines, encounter rates fall, disappointing visitors and reducing the perceived value of nature-based tourism products.
Ecosystem Services Dependency
Beyond direct wildlife viewing, tourism depends on ecosystem services that BII decline degrades. Water purification, pollination, natural pest control, and landscape aesthetics are all functions of intact biological communities.
The coral bleaching events threatening marine tourism in the Coral Triangle are a direct manifestation of biodiversity loss undermining a tourism-dependent ecosystem service.
The Restoration Imperative
Reversing BII decline requires not just protecting remaining intact ecosystems but actively restoring degraded ones. The UN Decade on Ecosystem Restoration (2021-2030) has catalyzed restoration commitments totaling 1 billion hectares, though actual implementation lags significantly behind pledges.
Tourism-funded restoration programs — where a portion of visitor fees directly finances habitat restoration — are demonstrating that tourism can be part of the solution. Costa Rica’s Payment for Ecosystem Services program, partially funded by tourism levies, has been instrumental in increasing the country’s forest cover from 21% in 1987 to 60% today.
Outlook
The BII trajectory will determine the long-term viability of nature-based tourism as a global industry. If current decline rates continue, an estimated 40% of existing nature tourism destinations will experience measurable degradation in their core wildlife assets by 2035. Investing in biodiversity restoration is therefore not merely an ethical imperative but an economic necessity for the tourism sector.