Winter Climate Change and the Northward Range Expansion of Tropical Invasive Plants in the Southeastern United States

Science Center Objects

Using temperature, species occurrence, field-based freeze damage data, and regression analyses for 84 invasive species, researchers at WARC are quantifying the species-specific relationships between minimum temperature and plant presence.

Objectives: We are using temperature, species occurrence, and field-based freeze damage data to investigate the following questions: (1) What is the sensitivity of Florida’s Category I Invasive Plant Species to freezing temperatures?; (2) What is the potential for range expansion of these species into the southeast region under alternative future climate scenarios?; and (3) Which protected lands in the southeast region are most vulnerable to warming-induced invasive non-native plant expansion? Although this work focuses initially on problematic species currently in Florida, the work is relevant to the entire southeastern United States. 

relationship between minimum temperature and Brazilian pepper presence

The relationship between minimum temperature and Brazilian pepper (Schinus terebinthifolius) presence. Area of maximum rate of change (AMRC) represents the upper and lower boundaries of the AMRC (i.e., the threshold zone, identified with the transparent gray box), and T represents the inflection point or discrete threshold level (middle vertical line within gray box) differentiating Brazilian pepper presence or absence (right and left side, respectively). Dashed lines represent 95% confidence bands. From Osland and Feher 2020.

Methodology for Addressing the Issue: Our approach is similar to recent work focused on Brazilian pepper range expansion (see Osland and Feher 2020), but we are applying it to the 84 species on the FLEPCC’s Category I Invasive Plant Species list.  Using temperature, species occurrence, field-based freeze damage data, and regression analyses for each species, we are quantifying the species-specific relationships between minimum temperature and plant presence. Field-based freeze damage observations will be used to assess the regression-based temperature thresholds. To illustrate the potential for invasive species range expansion, we will develop regional‐scale maps of the predicted temperature‐based probability of invasive plant presence under recent climatic conditions (1981–2010) and under three alternative future climate scenarios with warmer winter temperature extremes—a 2°C, 4°C, and 6°C increase in winter temperature extremes (e.g., see Osland and Feher 2020). 

The Science Issue and Relevance: Winter climate change is expected to lead to the tropicalization of temperate ecosystems, where tropical species expand poleward in response to a decrease in the intensity and duration of winter temperature extremes (i.e., freeze events). In the southeastern United States, freezing temperatures control the northern range limits of many invasive non-native plant species. Given the rich history of problematic plant invasions in the region, what is the potential for future range expansion due to climate change? The Florida Exotic Pest Plant Council (FLEPPC) has identified 84 species as Category I Invasive Plant Species, which are “altering native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives.” Many of these plants are tropical species that are sensitive to freezing temperatures, which means that they are expected to expand northward into other parts of the southeastern United States in response to warming winters. However, the effects of winter climate change on the range expansion of these species has been understudied. 

Brazilian pepper maps

Maps of the predicted temperature‐based probability of Brazilian pepper (Schinus terebinthifolius) presence under (a) recent climatic conditions (1981–2010) and three alternative future climate scenarios with warmer winter temperature extremes—a 2°C, 4°C, and 6°C increase in winter temperature extremes (b–d, respectively). From Osland and Feher 2020.