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Numerical simulation of the form and characteristics of Earth’s surface provides insight into its evolution. Landlab is an Open Source Python package that contains modularized elements of numerical models for Earth’s surface, thus reducing time required for researchers to create new or reimplement existing models. Landlab contains a gridding engine which represents the model domain as a dual graph of structured quadrilaterals (e.g., raster) or irregular Voronoi polygon-Delaunay triangle mesh (e.g., regular hexagons, radially symmetric meshes, fully irregular meshes). Landlab also contains components— modular implementations of single physical processes—and a suite of utilities which support numerical methods, input/output, and visualization. This contribution describes package development since version 1.0 and backward-compatibility breaking changes which necessitates the new major release, version 2.0. Substantial changes include refactoring the grid, improving the component standard interface, dropping Python 2 support, and creating 30 new components—for a total of 57 components in the Landlab package. We describe reasons why many changes were made in order to provide insight to designers of future packages. We conclude by discussing lessons about the dynamics of scientific software development gained from the experience of using, developing, maintaining, and teaching with Landlab. 

The emerging fungal pathogenBatrachochytrium salamandrivorans(Bsal) is a major threat to amphibian species worldwide with potential to infect many species if it invades salamander biodiversity hotspots in the Americas.Bsalcan cause the disease chytridiomycosis, and it is important to assess the risk ofBsal‐induced chytridiomycosis to species in North America. We evaluated the susceptibility toBsalof the common and widespread spotted salamander,Ambystoma maculatum, across life‐history stages and monitored the effect ofBsalexposure on growth rate and response of the stress hormone, corticosterone. We conclude that spotted salamanders appear resistant toBsalbecause they showed no indication of disease or infection, and experienced minor effects on growth upon exposure. While we focused on a single population for this study, results were consistent across conditions of exposure including high or repeated doses ofBsal, life‐stage at exposure, environmental conditions including two temperatures and two substrates, and promoting pathogen infectivity by conditioningBsalcultures with thyroid hormone. Exposure to high levels ofBsalelicited an acute but not chronic increase in corticosterone in spotted salamanders, and reduced growth. We hypothesize that the early acute increase in corticosterone facilitated mounting an immune response to the pathogen, perhaps through immunoredistribution to the skin, but further study is needed to determine immune responses toBsal. These results will contribute to development of appropriateBsalmanagement plans to conserve species at risk of emerging disease.