Rapid Northward Expansion of the Blacklegged Tick, <scp> <i>Ixodes scapularis</i> </scp> , in Response to Climate Change
Bibliographic record
Abstract
ABSTRACT Climate change rapidly drives species range dynamics, prompting many terrestrial organisms to shift northward to higher latitudes and forcing new species–species and species–environment interactions. The blacklegged tick, Ixodes scapularis , a biological vector of human pathogens including Borrelia burgdorferi (the bacteria causing Lyme disease), is undergoing rapid and persistent expansion into Canada, exposing new human populations to zoonotic diseases. Here, we used an ensembled forecasting approach to construct niche models of I. scapularis' current and future distribution and to identify the environmental drivers of habitat range. Georeferenced occurrence points were acquired from community science programs (eTick and iNaturalist) between 2017 and 2022 in Canada and the United States. We also collected high‐resolution environmental data using a spacing of approximately 1 km. We carried out 4704 model iterations across two datasets, 12 algorithms, and 10 climate profiles using 40 environmental variables. We extrapolated select models over three time periods, 2011–2040, 2041–2070, and 2071–2100, across two projected climate scenarios, SSP5‐8.5 and SSP3‐7.0, incorporating 2094 future outcomes of I. scapularis distribution. Our ensembles (AUC: 0.9565 ± 0.0065; TSS: 0.8435 ± 0.0155; Kappa: 0.819 ± 0.014) identified temperature, precipitation, biomass production (NPP), length of the growing season, climate moisture index, and number of yearly degree days as the variables that best explained I. scapularis distribution. Further changes to these climate conditions will result in continued I. scapularis range expansion, with, at the highest estimate, an increased niche area of ~248% (447,532 km 2 to 1,556,760 km 2 ) and, at the lowest estimate, by ~205% (409,475 km 2 to 1,247,689 km 2 ) before the turn of the century. These distributional niche changes coincide with a northern latitude limit reaching as far as ~48° N by 2040, ~50° N by 2070, and ~52° N by 2100. These findings highlight the invasive potential of I. scapularis , with implications for public health and changing ecosystem dynamics.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.003 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".