Four For Friday | Sept 5, 2025
LF186 | Depopulation vs biodiversity, McKinsey on healthspan, systems investing tookit and walkable US cities + AI tool: Chatbase
Welcome to this week’s Four For Friday - back from a month of travel in the US, Singapore, UK and France (and a two week LF break). Today’s stories cover the surprising environmental impact of depopulation (hint, it’s not positive), a systemic approach to healthspan from McKiunsey, a systems toolkit from MIT and data showing the impact of urban design on walking.
1. Depopulation - not the answer for the environment
One of the assumed advantages of the coming decline in population (two thirds of people globally live in countries with fertility rates below 2.1) is that at least the environment will recover. This may not be the case, at least in respect of biodiversity, according to this recent Nature paper.
The study looks at Japan's shrinking population and tracked 464 species across the rural landscape; despite human numbers falling in 41% of surveyed areas since 1995, biodiversity continued to decline. The culprit? Land-use changes accompanying depopulation - agricultural abandonment, urban sprawl, and farming intensification - prove more destructive than helpful. Only areas with stable human populations that maintained traditional rice farming showed biodiversity stability.
This research undermines the idea of “passive rewilding”; instead, active conservation strategies will be needed to halt ecological collapse accompanying our shrinking societies.
The So What? Countries expecting demographic decline to improve environmental problems need to develop more proactive - not passive - conservation strategies.
2. McKinsey on how to accelerate healthspan
New report by McKinsey on the biomedical aspects - drug development - of healthspan, which they call ‘healthspan science’. They note a big uptick in the investment (up 4x) and drug initiation (up 27%) over the past 5 years.
It suggests 7 ways to accelerate to healthspan science:
Field definition and perception. Establish a narrative that helps conveys measured optimism and is fully backed by science.
Fundamental understanding of aging biology. Orchestration of research supported by AI, machine learning (ML), and comprehensive data.
Biomarker consensus. Consensus on priority biomarkers as surrogate endpoints for clinical trials to benchmark interventions.
Translation and clinical development. Clinical expertise powered by AI-driven testing, novel trials and new data sets.
Regulatory pathways. New approval pathways to enable populations to access safe and effective innovative solutions.
Derisked investment. Research funders, pharma, and investors working alongside VC and HNW / philanthropists.
Evidence-based practice and talent. Developing global talent globally to accelerate public access to innovative interventions.
The So What? A succinct and practical systems approach to accelerating healthspan science.
3. A starter kit for systems investing
Speaking of systems change, this toolkit from MIT is a good primer on systemic investing, an approach that shifts finance from project-level bets to system-wide transformation.
Rather than chasing isolated returns, this encourages investors to identify leverage points, convene stakeholders, and deploy multiple forms of capital - financial, social, cultural - to drive transformational change.
The framework offers six stages (below from clarifying purpose to coordinating multicapital strategies, with practical tools such as ikigai mapping. It includes case studies of food systems, ocean economies, and climate tech.
The So What? MIT is one of the leading advocates of systems investing and this accessible guide will hopefully bring others into the mix.
4. What if every US city was as walkable as New York?
A Nature paper looked at data from 2.1 million US smartphone users and found that moving from a low- to high-walkability city increased steps by about 1,100 a day, while the reverse reduced activity by the same amount. Gains were sustained and concentrated in moderate-to-vigorous activity, equivalent to an extra hour of brisk walking per week.
Simulations suggest upgrading all US cities to New York-level walkability could allow 47m adults to meet aerobic health guidelines.
The So What? Useful data confirming New York’s walkability - and more generally, underscoring the role urban design has in population health.
Bonus AI Tip of the Week: Chatbase
Chatbase is a simple chatbot tool for corporate websites and solopreneurs.
That’s all for now - happy weekend everyone.
- Stephen