Partner review build Prepared for review by forestry, natural resources and public health partners. Not for public distribution. A warning map, not a post-mortem: the emerald ash borer front has not yet reached these counties.

Forest health · warning map

Black ash swamp vulnerability to emerald ash borer

Black ash is a foundation species of northern Minnesota wet forests. Emerald ash borer kills essentially every ash it reaches, and it has not yet reached these counties. This screen keeps three questions apart: how much ash is at stake, how soon the borer arrives, and what losing the ash does to the swamp.

Region: Beltrami, Cass, Clearwater, Hubbard, and Itasca counties, Minnesota.

  • 4,780of 31,750

    one-kilometre hexagons carry ash above the evidence floor

    inventory covers 27% of hexagons, the plant-community survey 30%, either 39%

  • 1,598

    priority hexagons: ash-bearing, hydrologically sensitive, front not yet arrived

    a modelled projection; the consequence axis is not validated

  • 273+ 175 infested

    hexagons on the detected front, plus those with a detection or inside the MDA generally infested area

    16 of 6,609 statewide detections fall in the region

  • 0.86AUC

    the exposure model on detections it never saw, 2021–2026 statewide (0.5 is chance)

    at the front threshold it catches 42% of 797 new-detection cells while calling 8% of the state exposed

Every hexagon, by category

31,750 hexagons · Beltrami, Cass, Clearwater, Hubbard, and Itasca

  • Infested 175
  • Front 273
  • High consequence 1,598
  • Buffered 2,734
  • Low ash 26,966
  • Unresolved 4

How to read the map

Three axes, kept apart

They are never collapsed into one number. Each axis is a weighted geometric mean of its factors, so a single fatal factor sinks the axis instead of being averaged away, and the factor doing the most damage is the one named. A missing measurement is skipped, never scored as zero.

Host

Cross-checked

How much ash is at stake. DNR forest-inventory species volumes on state land; the Native Plant Community survey where the inventory does not reach; the wetland inventory's hardwood-wetland class as a validated third tier. The popup names which tier produced each result.

Exposure

Validated

How soon emerald ash borer arrives. Distance to the nearest MDA detection, combined with MDA's own introduction-risk surface for human transport. Fitted and tested statewide on detections the model never saw, because only 16 detections fall inside the region.

Consequence

Projection

What losing the ash does. Organic and poorly drained soils, the mapped wetland footprint, and how much canopy would remain, ranked among the region's ash-bearing hexagons. No outcome data exist to test it, so it is labelled a projection everywhere it appears.

Every hexagon reports a category and a named driving factor. Infested: a detection in the hexagon or inside the MDA generally infested area. Front: exposure at or above the calibrated threshold. High consequence: ash-bearing, hydrologically sensitive, front not yet arrived. Buffered: ash present; replacement canopy or drier soils absorb the loss. Low ash: little ash in the evidence that covers it. Unresolved: no ash inventory, survey or wetland inventory covers it. Full method

What this map does not claim

The consequence axis is not validated. There is no post-mortality outcome dataset for Minnesota black ash swamps, so nothing on that axis has been tested against an observed outcome. It is a modelled projection from soils, the wetland inventory and the species that would remain, and it is labelled that way on the map, in the data and in the code.

Health is an adjacency, not a cause. Donovan et al. (2013) found ash loss from emerald ash borer associated with higher cardiovascular and lower-respiratory mortality across 15 states, among trees near where people live. These are mostly remote swamps. The CDC PLACES tract estimates shown here are for prioritisation where a hydrologic consequence and an existing burden coincide; they are not scored and are not a causal claim.

Honesty metrics

What was tested, and what was not

AxisStatusTestResult
Exposure Validated Temporal holdout, statewide. The model fitted on MDA detections through 2020 asked which 2 km cells would get their first detection in 2021–2026: 797 cells from 2,132 detections, against 54,801 undetected cells; 461 already-detected cells excluded. Parameters and the front threshold were fixed on an earlier window (through 2015 → 2016–2020) under a rule declared before the holdout was scored. Rank AUC 0.861 (distance alone 0.856; MDA introduction risk alone 0.740). At the front threshold of 0.558: sensitivity 0.42 against a base rate of 0.078 (lift 5.36). The same threshold gave sensitivity 0.75 at base rate 0.031 on the calibration window: 2021–2026 arrivals jumped further from the prior record than 2016–2020 ones did.
Host Cross-checked Two DNR datasets describe ash independently: forest-inventory species volumes on state land, and the Native Plant Community survey. Compared where both cover at least half a hexagon (2,566 hexagons). Not an outcome validation. Agreement 91% (kappa 0.36). Inventory ash share ranks survey ash-swamp hexagons at AUC 0.90; the survey ranks inventory ash hexagons at AUC 0.89. Disagreements: 180 hexagons ash by inventory only, 54 by survey only. Reported, not reconciled. The wetland-inventory hardwood tier scored AUC 0.81 against the inventory and 0.85 against the survey and was kept as the third tier.
Consequence Projection None possible. No post-mortality outcome data exist for Minnesota black ash swamps. Not validated. The consequence axis is a modelled projection. No post-mortality outcome data exist for Minnesota black ash swamps, so nothing on this axis has been tested against an observed outcome. Factor bands are literature-based or stated assumptions.

Method in brief

Public data, declared rules, published misses

The unit is the same 1 km hexagon grid as the traditional-foods habitat screens, so results are geographically comparable. Ash comes from DNR forest-inventory species volumes (state land only) and the DNR plant-community survey; Mountain-Ash is Sorbus, not an ash, and is excluded. Exposure is distance to the nearest MDA detection with MDA's introduction-risk class as a covariate, chosen under a selection rule declared before the holdout was scored. Consequence ranks soils, wetland and replacement canopy among ash-bearing hexagons. Recency weighting, closed-depression detection and drinking-water proximity were specified, evaluated or deferred, and each is recorded with its reason.

About the screen: method, ecology, economics, cultural context