Weekly clearing alerts vs. annual land-cover maps: what changes
Most forest-monitoring programs still run on the same clock. A land-cover map lands once a year, usually months after the growing season it describes, and the team spends the next quarter reconciling it against whatever already happened on the ground. That lag is the whole problem a weekly clearing feed is built to close.
What an annual land-cover map actually tells you
An annual update is a classification built from the best cloud-free composite the sensor record gives you for that year, delivered on a cycle that runs six to twelve months behind the calendar it describes. It's the right tool for a stock number: total forest cover in a jurisdiction, forest-to-non-forest ratios by district, a trend line you can show across five or ten reporting years. Donors and regulators asking for an annual figure want exactly this kind of map, and nothing about weekly monitoring replaces it.
What it doesn't do is tell you when something happened. A polygon that shows up as "cleared" in this year's composite could have lost canopy in February or in November. By the time the map ships, the cutting crew, the skid trail, and the truck that hauled the logs out are long gone. For a compliance team trying to trace a shipment back to a cutting date, that's not a small gap.
What changes when the alert comes weekly
A weekly clearing alert works off a different unit entirely. It checks the area you've drawn against each new cloud-free pass as it comes in and flags a change within days of that pass. The output is a list: this polygon, this week, flagged.
That distinction matters most to two kinds of teams. An enforcement unit screening a concession boundary gets a name on a list while the clearing is still recent enough to send someone out. A trader's sustainability team screening a supply shed gets the same thing for a different reason: a cutting block shows up on the feed before the harvest from that block reaches the mill, which is the window where a sourcing decision still changes anything. Neither of those windows exists once you're reading an annual tally.
Where each one still earns its keep
Annual land-cover maps are not obsolete. They're the right instrument for area accounting, for a baseline you report against year over year, for answering "how much forest did this jurisdiction have in 2023 versus 2024." Weekly alerts don't replace that denominator, they feed it. Most teams that run both end up using the annual map as the yearly stocktake and the weekly feed as the stream of individual events that eventually roll up into next year's number.
The failure mode is using one where the other is needed. A regulator using only an annual map to screen active clearing finds out about it a year late, after the timber has moved. A trader using only a weekly feed with no annual baseline has a list of flags but no sense of which areas were already degraded going into the year, and no clean denominator for a sustainability report.
The practical split
An annual map answers how much forest is left in a jurisdiction. A weekly feed answers whether anything changed in a specific draw area this week, and that second question is the one Deforestation Alerts is built around: a weekly clearing alert scoped to the forest area or supply shed you define, flagged within days of the first cloud-free look, routed as a list an enforcement or sourcing team can work from.
If your team is still catching clearings a year late, it's worth seeing what a weekly feed on your own AOI looks like.