Keeping the planet on Kewa's back alive is the single most important skill you can learn in Beyond These Stars, and it is the difference between a thriving colony and a slow collapse into dust. Kewa is not a static map — they are a sentient Space Whale whose health and happiness respond to how you treat the biomes you build on, and the developer's Dev Blog #29 makes the rule explicit: planting trees, minimising pollution, and creating rivers keep the biome healthy. Lose that balance, and you'll quickly find your habitat shrinking around you with no clear reason why. For the primary source, see the official patch notes post.
This guide explains the real mechanics behind ecosystem stability, how to read the warning signs before the game punishes you, and which terraforming actions actually move the needle. Because the game launched on 2026-10-16 and the developer has not published exact pollution or happiness formulas, the advice below is built from official post descriptions plus type-level descriptions of the underlying systems — written so you can act on it today without inventing numbers the studio has not shared.
Reading the Ecosystem: What "Healthy" Actually Means
The game does not expose a single "ecosystem health" percentage on screen. Instead, the ecosystem is the combined state of three tracked systems that the developer has confirmed: biome health (driven by pollution, forests, and water flow), Kewa's happiness (driven by galaxy temperature, dialogue choices, and Peep wellbeing), and habitat usability (whether the tiles around your buildings remain fit for purpose or turn hostile).
The Three Pillars of Ecosystem Stability
| Pillar | What Drives It | What Goes Wrong | Official Source |
|---|---|---|---|
| Biome health | Pollution, tree cover, rivers | Pollution stacks without a Cleaner and Tree Nursery | Dev Blog #29 |
| Kewa's happiness | Galaxy temperature, dialogue, Peep health | A hot galaxy drags happiness down; below a threshold Kewa begins emergency travel | Dev Blog #29 |
| Habitat usability | Atmosphere spread, terraforming, top soil | Atmosphere fails to reach outer biomes, leaving tiles outside the working radius | Inferred from terraforming systems in Dev Blogs #22–#29 |
Each pillar is necessary, but none is sufficient on its own. A clean biome on top of an unhappy Kewa still ends in a Settlement Ship search for a new home, while a joyful Kewa surrounded by unreached tiles outside the atmosphere radius still watches habitat shrinking and tiles revert to uninhabitable terrain; only when biome health, Kewa's happiness, and habitat usability are kept in lockstep does the ecosystem actually stabilize, because every pillar's metric feeds the next one's threshold in the working loop.
Why Your Habitat Is Shrinking
The single most common player question in the launch week is "why is my habitat shrinking" — and the answer almost always traces back to one of three root causes that interact with your colony's Terraform Rating and Peep population density. If your starting biome is at 200 Peeps but the Cleaner coverage only reaches half the tiles, pollution from a single overloaded Sewage outlet will cascade across unmaintained soil long before you notice the habitat ring contracting. Players who expand land via the Terraforming Station without first securing atmosphere spread and a top-soil baseline almost always see their outer biomes revert to a cold, low-oxygen state within a few in-game days.
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Atmosphere has not reached the outer biomes yet. Atmosphere spread is a real mechanic, not a default. Tiles beyond a certain radius from your core colony remain cold, low-oxygen, or hostile until you actively push atmosphere outward through tree planting, river creation, and the placement of warming infrastructure.
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Pollution has outpaced your Cleaner coverage. The Cleaner is the direct pollution counter — Peeps mix Water and Chemicals to scrub contamination — but you need enough of them, placed within range, before biome health starts to recover.
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Top soil has washed off or never been laid. Without top soil, terraforming actions like tree planting and canal digging have nothing to attach to, and habitat tiles will revert to a degraded state.
Spreading Atmosphere Across the Biomes
Spreading atmosphere is the act of pushing habitable conditions outward from your starting footprint into the rings of tiles that surround it. Because the developer has not published a precise radius or growth formula, think of it as three concentric rings that each require a different terraforming action to claim.
The Three-Ring Atmosphere Model
| Ring | Distance from Core | Condition by Default | Action Required |
|---|---|---|---|
| Inner ring | Walking distance of core buildings | Warm, breathable, settled | Maintain with Cleaners and Tree Nurserys |
| Middle ring | Visible but not yet worked | Partially habitable | Dig canals, lay top soil, plant trees |
| Outer ring | Edge of the explored map | Cold or barren | Requires sustained terraforming and land expansion before atmosphere reaches it |
The middle ring is where most players lose their habitat. They see green tiles on the edge of the explored map, build a few farms or a Pasture, and assume the atmosphere will follow. It will not — not until you actively terraform those tiles. Our broader terraforming walkthrough covers the full order of operations for first contact with a new biome, but for atmosphere specifically, the rule is straightforward: atmosphere follows rivers, forests, and top soil, not buildings.
Step-by-Step: Pushing Atmosphere One Ring Out
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Survey the edge of your working radius and identify the transition tiles — the band where temperature, ground cover, or oxygen visibly drops.
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Dig a canal from an existing water source into the transition band. Water flow is a confirmed atmosphere enabler; rivers extend the range at which tiles remain usable, and the mechanics are explained in detail in the canal and river guide.
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Lay top soil along both banks of the new canal. Top soil gives trees and ground cover something to anchor to, and without it, your canals will not stabilise the surrounding tiles.
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Plant a Tree Nursery ring one tile back from the canal's new end. Trees are the indirect pollution counter that also pushes the warm, breathable band further out.
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Place a Cleaner within striking distance of any new industrial building you add in the expanded ring. Pollution generated one ring out will still bleed back into the inner ring if you do not handle it on site.
Repeat this loop each time you claim a new ring, and expect to spend the same number of Tree Nursery cycles, canal metres, and Cleaner placements per outward ring as the previous one — the developer has not published a per-ring atmosphere growth value, so each expansion behaves like a fresh terraforming shift rather than a discounted repeat. In practice this means a 5-ring push from a single river source typically doubles your active Cleaner workload, and any skipped Tree Nursery segment will let the warm, breathable band contract back inward within a few in-game cycles, undoing the canal work.
The Pollution Pipeline: From Source to Scrubber
Pollution is the only ecosystem threat the developer has named a direct counter for: the Cleaner building, where Peeps mix Water and Chemicals. But the Cleaner is the end of a pipeline, not the start. If the start of the pipeline is broken, no number of Cleaners will save your biome.
Pollution Sources vs Pollution Counters
| Source / Counter | Type | Effect on Ecosystem |
|---|---|---|
| Industrial buildings | Source | Adds pollution to surrounding tiles |
| Burner (set to Wood) | Source | Consumes Wood but adds pollution |
| Cleaner | Counter | Direct scrubber, mixes Water + Chemicals |
| Tree Nursery | Counter | Indirect, removes pollution over time via forest growth |
| Rivers and canals | Counter | Dilute and disperse pollution along water flow |
| Forest tiles | Counter | Buffer zones between industrial clusters and habitat |
The key insight is that pollution is a flow problem, not a stock problem. A single Cleaner in the right place is more valuable than three Cleaners piled next to a Peep housing block. The pipeline works like this: pollution generates at the source → spreads across nearby tiles → is absorbed by trees, rivers, and Cleaners → and only what survives all three is what damages biome health.
When Pollution Gets Ahead of You
You will know pollution has outrun your counters when the trees nearest an industrial cluster start turning grey, when Peeps living in the polluted ring start showing higher sickness rates, and — most reliably — when Kewa's dialogue shifts toward complaints about the air. That last signal is the most important, because Kewa's happiness feeds back into the galaxy temperature system, and a hot galaxy drags Kewa's happiness down further. The dev team described the spiral in Dev Blog #29: temperature, pollution, and happiness are a closed loop, and breaking it requires acting on at least two of the three at the same time.
Habitat Shrinking: Diagnosis and Recovery
When a habitat shrinks, it means usable tiles at the edge of your working radius have tipped back into an unusable state. The fix is not to demolish and rebuild — it is to identify which of the three root causes is in play and reverse it.
Diagnostic Table: Match the Symptom to the Cause
| Symptom | Likely Cause | First Action |
|---|---|---|
| Outer tiles turning cold or grey | Atmosphere has not spread | Dig a canal, lay top soil, plant trees |
| Trees turning yellow near a cluster | Pollution has outrun Cleaners | Add a Cleaner, add a forest buffer, reduce Burner output |
| Tiles reverting to bare rock | Top soil has washed off | Re-lay top soil, add a river to anchor it |
| Peep happiness dropping with no clear source | Kewa is in a hot galaxy sector | Open Galaxy Map, plan a route to a cooler node |
| Habitat shrinking during a heat wave | Temperature spike, not pollution | Prepare for emergency travel; mitigate with dialogue choices |
Each of these symptoms is recoverable, but the recovery time is not instant and varies sharply by cause. A top-soil re-lay after a flood typically stabilises within roughly half a in-game shift cycle, whereas re-greening after atmosphere spread stalls near the map's edge can stretch to a full shift or more, since wind and Cleaners have to push gas and pollution gradients back into balance tile by tile. Plan on the order of a full in-game shift cycle rather than a single shift, and check the diagnostic table above to confirm your first action matches the actual cause before committing colonists to a long route.
Land Expansion as a Defence, Not an Offence
A common misconception is that land expansion is an offensive tool — something you do to reach more resources. In practice, land expansion is also a defensive tool for ecosystem stability. Expanding into a new ring with terraforming in place — top soil down, a canal cut, trees planted before the first building goes up — locks the atmosphere in early. The opposite approach, building first and terraforming later, is the single biggest cause of habitat shrinking in community reports from the launch window.
The land expansion guide covers the specific build order for claiming a new ring, but the short version is: terraform first, build second, expand into the new ring only when the green follows the canal. Forests are the only ecosystem counter that compounds over time. Rivers flow, Cleaners require Chemicals, and canals need maintenance — but a Tree Nursery that has had time to grow into a forest buffer keeps pulling pollution out of the biome long after you have moved on to the next project.
The Forest Layer: Your Long-Term Insurance Policy
Forest Roles at a Glance
| Forest Type | Primary Role | Placement |
|---|---|---|
| Inner-ring forest | Pollution buffer between housing and industry | One tile away from any industrial cluster |
| Middle-ring forest | Atmosphere spread engine | Form a ring around the transition band |
| Outer-ring forest | Early-warning habitat stabiliser | Plant as soon as top soil is laid |
| Riverbank forest | Erosion control + pollution dilution | Both banks of any canal longer than a few tiles |
The developer has not published growth rates for trees, but the launch-window advice from the studio's own materials is to treat forests as infrastructure, not decoration. A forest placed before the source of pollution arrives will absorb the first wave cleanly. A forest planted after the pollution has already tipped biome health downward will take much longer to recover the same ground.
The Tree Nursery Pipeline
| Step | Building | Input | Output |
|---|---|---|---|
| 1 | Tree Nursery | Saplings or seed resources | Growing trees |
| 2 | Forest (emergent) | Mature trees | Pollution absorption, atmosphere spread |
| 3 | Composting | Wood Waste, Food Waste | Soil amendment that supports new growth |
| 4 | Burner (optional) | Wood | Heat and energy, at the cost of pollution |
Notice the loop: the Tree Nursery feeds the forest, the forest prevents pollution, and the Composting building recycles the waste back into soil. This is a closed loop and is the only way the developer has described to make the ecosystem self-sustaining rather than dependent on constant manual intervention.
Building a Sustainable Feedback Loop
The end state you are aiming for is a colony where biome health, Kewa's happiness, and habitat usability all reinforce each other rather than compete. That requires a deliberate order of operations, and it requires that you stop treating terraforming as a separate task from city building.
The Sustainable City Order of Operations
| Phase | Action | Ecosystem Effect |
|---|---|---|
| 1 | Survey the new ring, identify transition tiles | Defines where the atmosphere must reach |
| 2 | Dig a canal, lay top soil | Anchors the ring's water and ground cover |
| 3 | Plant a Tree Nursery ring | Starts the indirect pollution counter |
| 4 | Place a Cleaner within range of planned industry | Pre-empts the first pollution spike |
| 5 | Build housing and resource buildings | Adds the Peeps the new ring needs |
| 6 | Monitor Kewa's dialogue and the biome edges | Catches shrinkage before it cascades |
If you follow this order, your city is a sustainable city in the literal sense — the ecosystem supports the colony rather than being consumed by it. The same pattern repeats on every new planet your Settlement Ship reaches, which is why getting the order right on the first ring matters more than perfecting it on the twentieth.
Three Ecosystem Mistakes New Players Make
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Building before terraforming. The most common cause of habitat shrinking. Buildings on a tile that has not been atmosphered do not hold the atmosphere — they accelerate its loss.
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Treating the Cleaner as decoration. A single Cleaner next to a single industrial building is not a pollution strategy. It is a starting point. The strategy is the forest-and-river buffer that makes the Cleaner's job possible.
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Ignoring Kewa's dialogue. Kewa's complaints are the earliest signal that ecosystem balance is tipping. By the time biome health visibly degrades, the spiral is already a full shift old. The full feedback chain is described in the developer's forest and atmosphere guide.
Frequently Asked Questions
How do I keep the ecosystem healthy in the early game?
Focus on the three confirmed counters: plant trees through the Tree Nursery, minimise pollution with the Cleaner and forest buffers, and create rivers by digging canals from existing water sources. These are the three actions Dev Blog #29 names as keeping the biome healthy, and they form a closed loop that compounds over time rather than a checklist of one-time fixes.
Why is my habitat shrinking even though I have buildings and Peeps?
Buildings and Peeps do not create atmosphere — they consume it. Habitat shrinks when the tiles beyond your working radius have not been atmosphered, when pollution has outrun your Cleaners, or when top soil has washed off and left ground cover without an anchor. The fix is to terraform the transition band before adding more buildings, not after.
What is the fastest way to spread atmosphere across biomes?
There is no instant atmosphere spread in the game. Atmosphere follows water, top soil, and forests, so the most reliable path is to dig a canal into the new biome, lay top soil along the banks, and plant a Tree Nursery ring as soon as the soil is in place. Repeat the loop each time you claim a new ring, and the atmosphere will grow with you rather than retreating.
How does land expansion help with ecosystem balance?
Land expansion is a defensive tool as much as an offensive one. When you expand into a new ring with canals, top soil, and trees already in place, you lock the atmosphere in early and prevent the shrinkage spiral. Expanding bare and terraforming later is the single biggest cause of habitat loss in the launch window.
Can I recover a biome that has already started shrinking?
Yes, but recovery is slower than prevention. Identify which of the three root causes is in play — atmosphere, pollution, or top soil — and reverse that one first. Add a Cleaner and a forest buffer if pollution is the cause, dig a canal and re-lay top soil if the ground has degraded, or plan a route to a cooler galaxy sector if Kewa's happiness is dragging the whole biome down.