Bark Beetle Risk Map

How far ahead does it work?

Forecast made	Share of attacks in riskiest 10%
October before the season	29%
April, same year	30%
June, same yearMay include attacks already started	34%

Dead-spruce test, riskiest 10%	2021 photos	2023 photos
One season ahead	62%	39%
Two seasons ahead	35%	32%

With no skill, each share would be about 10%. This map is the October forecast. Maps for April, June and two seasons ahead are not built yet. Later dates help only slightly, and skill falls with a longer lead.

Where 2024 dead spruce lies on this map

Area, riskiest 10%	All dead-spruce cells	New cells

This shows agreement with later detections, not forecast skill. By our labelling rule, trees in a 2024 photo mostly died from attacks up to 2023, the same year as the map's inputs. B5+ also trained on examples from 2024 photos, 58 in AOI-1 and 43 in AOI-2, and the index did not. Leaving out cells within 500 m of those examples moves the B5+ new-cell share from 40% to 39% in AOI-1 and stays at 42% in AOI-2. Detections need a 2024 photo, so places photographed in other years look clean, and Östergötland has no 2024 photos. These are AI detections of medium or high confidence.

How far to trust it

Field test	Index	B5+
Östergötland, AUPRC	0.182	0.227
Östergötland, attacks in top 10%	24%	29%
Forward 2023, AUPRC	0.110	0.248
Forward 2023, attacks in top 10%	19%	32%

SLU field plots: Östergötland has 418 plot-years with 38 attacks, and forward 2023 has 994 with 63. B5+ is clearly better than the index in forward 2023. In Östergötland the two cannot be told apart.

About this map

The model is B5+, trained across all areas on SLU plots from before 2024 and dead-spruce examples with label years before 2024. Those examples include 2024 photos, which did not exist in spring 2024, so this map could not have been issued then.

The forest mask is NMD 2018 forest of all types, so it includes pine and broadleaf stands. Limiting the map to spruce-rich forest would hide real attacks: a third of attacked plots have under 25% spruce on the land-cover map within 50 m.

The satellite background is a Sentinel-2 summer 2023 composite at 20 m, so it shows fields and towns but not single trees. SLU plot positions are confidential and are not on this map.

Sources: Skogsstyrelsen (risk index, dead-spruce detections), Naturvårdsverket NMD 2018, SCB (boundaries), Copernicus Sentinel-2 2023 via Microsoft Planetary Computer. Coordinates are SWEREF 99 TM.

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