When people think about biodiversity, they usually imagine endangered species, national parks, or forests. When they think about social capital, they think about trust, friendships, or community. Rarely are these two concepts discussed together. Yet our latest research suggests that they may be more closely connected than we previously thought.
A surprising question
One of the strongest predictors of economic opportunity is social capital.
Research by Raj Chetty and colleagues has shown that people who grow up in communities where individuals from different socioeconomic backgrounds interact are more likely to move up the income ladder. These cross-class connections—what economists call economic connectedness—matter enormously for equality of opportunity.
But where does social capital come from?
Economists have traditionally looked at education, income, institutions, demographics, and urban design. Ecology has rarely entered the conversation.
We wondered whether biodiversity itself might be part of the answer.
Looking beyond the economy
Our study analysed hundreds of U.S. cities by combining measures of protected natural areas with data on economic connectedness from Opportunity Insights.
Rather than asking whether biodiversity simply increases social capital, we asked a more subtle question:
Is biodiversity a necessary condition for high social capital?
This distinction is important.
Something can be necessary without being sufficient.
A car needs fuel to move, but fuel alone does not make it drive. Likewise, biodiversity may be required for communities to achieve high levels of social capital, even though many other factors also influence whether that potential is realised.
To answer this question, we used Necessary Condition Analysis (NCA) alongside Qualitative Comparative Analysis (QCA)—two methods rarely applied together in ecological economics.
What we found
The results were surprisingly consistent.
Across U.S. cities, biodiversity emerged as a necessary—but not sufficient—condition for high neighbourhood economic connectedness.
In other words:
- Cities with strong social capital almost always had a minimum level of surrounding biodiversity.
- However, simply increasing biodiversity did not automatically produce stronger social capital.
This is an important distinction.
Trees alone do not create trust. Parks alone do not create friendships. Protected areas alone do not eliminate inequality. Instead, biodiversity appears to provide part of the environmental foundation upon which social relationships can develop.
Why might biodiversity matter?
There are several possible explanations.
Biodiverse environments create spaces where people meet, exercise, spend leisure time, and interact with neighbours. These encounters increase opportunities for informal conversations, community participation, and relationship building.
Healthy ecosystems also improve wellbeing, reduce stress, encourage outdoor activity, and make neighbourhoods more attractive places to live. Over time, these effects may strengthen social networks that help individuals access information, jobs, education, and opportunities.
In other words, biodiversity may indirectly support the social infrastructure that allows communities to thrive.
But biodiversity is not enough
One of the most interesting findings is what we didn’t find.
Our Qualitative Comparative Analysis showed that biodiversity alone could not explain why some communities enjoy high social capital while others do not. Education, demographic composition, income distribution, population characteristics, and urban context all remain important. This means policymakers should avoid simplistic conclusions.
Creating a park will not automatically reduce inequality.
Planting trees alone will not solve social fragmentation. Instead, biodiversity should be viewed as one ingredient within a broader system that includes education, housing, inclusive public spaces, transport, and economic opportunity.
A new way of thinking about biodiversity
Perhaps the most important lesson is conceptual. Environmental policy often treats biodiversity as something that protects wildlife. Economic policy often treats social capital as something generated by institutions.
Our findings suggest these two worlds should not be separated.
Biodiversity may contribute to the social conditions that support economic development, mobility, and collective action. Rather than viewing nature solely as an environmental asset, we should also recognise its potential role as a form of social infrastructure.
What this means for policymakers
For governments, the message is straightforward.
Conservation policy should not be viewed only as environmental spending.
Protecting biodiversity may generate wider social benefits by supporting healthier, more connected communities.
Urban planning should integrate biodiversity into neighbourhood design, recognising that accessible green and protected spaces may contribute to long-term social cohesion.
Social policy should also recognise that environmental quality and community wellbeing are interconnected rather than separate policy domains.
While biodiversity alone cannot eliminate inequality, neglecting it may remove an important foundation upon which stronger communities are built.
What still needs to be understood?
Like all research, our study raises as many questions as it answers.
Does biodiversity directly increase social capital, or do prosperous communities simply invest more in conservation?
Which ecosystems matter most?
Do urban parks have the same effects as larger protected areas?
Are these relationships similar in Europe, Asia, or developing countries?
Understanding these mechanisms will require collaboration between economists, ecologists, sociologists, psychologists, and urban planners.
That is precisely why this research matters.
The bigger picture
For decades, economics has largely viewed biodiversity as a source of ecosystem services or natural capital.
Our research suggests another possibility—that biodiversity may also shape how societies connect, cooperate, and create opportunities. It may not be sufficient to build social capital—but it could be one of the conditions without which strong, connected communities struggle to emerge.
As environmental degradation accelerates worldwide, protecting biodiversity may therefore become more than a conservation goal.
It may also become an investment in stronger societies.
Reference
Auza, A., & Fuinhas, J. A. (2025). No social capital without biodiversity. Applied Economics Letters. https://doi.org/10.1080/13504851.2025.2489780