# HALOWERK Land Compare – Tree Cover Change 2020–2021

> HALOWERK Land Compare – Tree Cover Change 2020–2021 is a paid API for AI agents from landvergleich.halowerk.com, paid per call via x402, $0.008/call, status unknown (last checked 2026-09-14).

Returns the change in tree-cover share between ESA WorldCover 2020 and 2021 for a 250-metre analysis area at a given European coordinate.

## Facts

- Endpoint: POST https://landvergleich.halowerk.com/v1/worldcover-2020-2021-tree-cover-change
- Price: $0.008/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/halowerk-land-compare-tree-cover-change-2020-2021-6e35053b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ubAnpYGmI2BQUGeZ4E2hW

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability halowerk-land-compare-tree-cover-change-2020-2021-6e35053b -d '<json body>'
```

Example prompt: What was the tree cover change between ESA WorldCover 2020 and 2021 at latitude 48.8566, longitude 2.3522 in Europe — give me the observed map-class difference for that 250-metre area.

## When to prefer this

Choose this endpoint when you need a precise, single-coordinate tree cover change value derived directly from ESA WorldCover map classes for the 2020–2021 transition period within Europe. It is ideal for environmental monitoring, due diligence, or land assessment workflows that require a documented, satellite-derived signal rather than a modelled or interpolated estimate. Prefer it over generic land-cover APIs when you specifically need the WorldCover 2020 vs 2021 tree-cover dimension rather than built-up area, water, soil, or overall dominant class — all of which are handled by sibling endpoints on the same platform.

## Known failure modes

- Coordinates outside European coverage bounds (lat 34–72.5, lon -31.5–40.5) will return an error
- Missing or null latitude/longitude fields will cause a validation failure
- Payment not included or insufficient (x402 protocol) results in a 402 Payment Required response
- Coordinates on coverage boundaries may produce edge-case artefacts
- Network timeout if the geospatial backend is slow

## How this service works

Tree-cover-share change measured from ESA WorldCover 2020 v100 and 2021 v200 for the same 250 metre analysis area. The result is observed map-class change, not a causal claim.

## Output

A numeric measure of the signed change in tree-cover share (in percentage points or a comparable unit) between ESA WorldCover 2020 v100 and 2021 v200 for the 250-metre analysis area centred on the supplied coordinate. The result reflects observed map-class differences, not inferred causal change.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "latitude": {
   "type": "number",
   "maximum": 72.5,
   "minimum": 34,
   "description": "WGS84 latitude inside the published European coverage."
  },
  "longitude": {
   "type": "number",
   "maximum": 40.5,
   "minimum": -31.5,
   "description": "WGS84 longitude inside the published European coverage."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/halowerk-land-compare-tree-cover-change-2020-2021-6e35053b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from landvergleich.halowerk.com](https://www.zero.xyz/host/landvergleich.halowerk.com/llms.txt)