Out of the weeds? Reduced plant invasion risk with climate change in the continental United States

Abstract

Identifying invasion risk is critical for regional prioritization of management and monitoring, however, we currently lack a comprehensive assessment of the invasion risk posed by plants for the United States. We aim to quantify geographic invasion risk for currently established terrestrial invasive plants in the continental U.S. under current and future climate. We assembled a comprehensive occurrence database for 896 terrestrial invasive plant species from 33 regional collections of field and museum data and projected species ranges using MaxEnt species distribution models based on current (1950-2000 average) and future (2040-2060 average) climate. We quantified geographic invasion risk as differences in species richness, invasion debt, range infilling, and identification of hotspots. Potential invasive plant richness was higher than observed richness, particularly in eastern temperate forests, where as many as 83% of species with suitable climate have not yet established. A small percentage (median = 0.22%) of species' potential ranges are currently occupied by them. With climate change, potential invasive plant richness declined by a median of 7.3% by 2050. About 80% of invasive plant hotspots were geographically stable with climate change, with the remaining 20% shifting northward. Invasion hotspots and current invasion debt reveal extensive, ongoing risk from existing invasive plants across the U.S., particularly in the Southeast. Climate change alters the spatial distributions of focal species for monitoring and is likely to reduce overall invasion risk in many areas. Early detection and rapid response programs could be most effective in stemming the spread of invasive plant species in areas with increased risk under climate change, while areas with persistent high risk are candidates for containment and control. The areas with reduced risk are prime locations for invasion of new imports from tropical and subtropical climates, highlighting the simultaneous need for prevention strategies.

Climate change both facilitates and inhibits invasive plant ranges in New England

“…An unexpected finding from our study was the predicted decline of A. petiolata in southern NE under future climate warming. Our illustration shows that climate change may mitigate invasions (2,8); however, this mitigation is not an apparent benefit but rather, a red flag. Although A. petiolata may decline considerably in NE, invasion risk remains high in northern NE and southern Canada.…”

“…4 discusses the influence of extreme weather events). Existing studies have relied primarily on correlative range models (species distribution/ niche/climate envelope models) to forecast how habitat suitability might change with climate (5)(6)(7)(8), often because mechanistic approaches are more data hungry. However, forecasting invasions and other nonequilibrium scenarios necessarily requires predictions in locations that are either geographically or environmentally different from where the species has been observed, which is precisely where occurrence datasets are lacking.…”

Incorporating climate change into invasive species management: insights from managers

“…For example, the geographic ranges of some invasive species are expected to shift poleward and upward in elevation as the climate warms (Dukes and Mooney 1999;Bradley et al 2010), adding new species to those currently being managed. As a result, higher latitude areas, such as the Northeastern U.S., are likely to become 'hotspots' of invasion with increased numbers of problematic species (Allen and Bradley 2016). Additionally, climate change stresses native ecosystems (Bellard et al 2012) and increases disturbances through climate extremes (Diez et al 2012), potentially creating new opportunities for introduced species to establish and thrive.…”

Global distribution patterns and niche modelling of the invasive Kalanchoe × houghtonii (Crassulaceae)

“…The latter observation agrees with multi-species studies of plant invaders in the United States (896 spp.) 104 and Australia (72 spp.) 105 , and probably reflects that continental areas would tend to undergo more severe climatic changes than coastlines.…”