Overview of Why are scientists planting tiny forests in big cities?
This NPR Short Wave episode explores microforests—small, densely planted forest patches designed for urban spaces—and why scientists are using them to help cities cope with climate change. Producer Rachel Carlson visits a microforest at Ascot Hills Park in northeast Los Angeles, where researchers are testing how native plantings can boost biodiversity, suppress weeds, cool neighborhoods, and absorb carbon dioxide.
What a microforest is
A microforest is a small, human-designed forest ecosystem planted in a compact urban footprint.
Key characteristics
- Tiny scale: usually about 200 square feet to 1 acre
- Dense structure: multiple layers of plants, from shrubs and understory plants to canopy trees
- Forest-like function: the tree canopies connect and create a layered habitat similar to a natural forest
- Fast growth: matures much faster than a traditional forest, often in a few decades instead of a century
Where the idea came from
The concept traces back to Japan and ecologist Dr. Akira Miyawaki, who developed a method for restoring degraded land by planting dense clusters of native species all at once.
Why scientists plant microforests in cities
Microforests are meant to do more than just add greenery. Researchers use them to:
- Restore biodiversity with native plants
- Cool urban neighborhoods
- Improve soil health and air quality
- Create habitat for birds, insects, bats, and other wildlife
- Help cities adapt to drought and climate change
In Los Angeles, that means choosing drought-tolerant native species like:
- Southern California black walnut
- Blue elderberry
How the LA microforest works as an experiment
The Los Angeles site is especially useful because researchers can compare it to a nearby control plot of the same size that remains filled with invasive weeds.
What the researchers study
- Which insects, birds, lizards, mice, and spiders appear
- How quickly the plants grow
- Which species thrive together
- Whether the microforest crowds out weeds naturally
Tools they use
- GPS mapping of individual plants
- Drones to measure growth and plant volume
- Spiderweb DNA sampling to detect animals passing through
- A community science app that lets visitors scan QR codes and report plant height and health
What they found
The microforest appears to be working well.
Notable results
- Over 100 animal species documented in the microforest
- Roughly 89% plant survivorship
- About 80% reduction in weeds compared with earlier stages
- Roughly 1 metric ton of carbon removed per year, with projections of 50+ metric tons per year over two decades
The episode emphasizes that the microforest is not just “looking green” — it is behaving like a functioning ecosystem.
Why this matters
The scientists argue that microforests can be a practical tool for cities because they:
- Turn small unused or degraded spaces into functioning habitat
- Offer measurable ecological benefits in a short amount of time
- Bring nature closer to people in densely built areas
- Provide a scalable model for urban climate resilience
Main takeaway
Microforests are a compact, science-backed way to rebuild ecological function in cities. By planting dense layers of native species in small spaces, researchers can create mini-ecosystems that support wildlife, store carbon, reduce weeds, and make hot urban environments more livable.
Notable insight
“You’re kind of planting a whole ecosystem at one time.”
That idea captures the core of the episode: microforests are less about landscaping and more about rapid ecosystem restoration.