Taylor, S. & Kumar, L. (2014). Climate change and weed impacts on small island ecosystems: Lantana camara L. (Magnoliopside: Verbenaceae) distribution in Fiji. Pacific Science, 68(1), 117-133. https://doi.org/10.2984/68.1.11

Summary

Island ecosystems in the Pacific are particularly vulnerable to the impacts of invasive species, and climate change is expected to intensify these impacts. We have little information, however, on how the distribution of most invasive species may shift under a future climate. Lantana (Lantana camara) has been ranked as one of the world’s 100 worst invasive species due to its impacts to agriculture, timber production, and natural ecosystems. It is also considered among the most invasive species found on the majority of the Islands in the Pacific Region and it is unclear how it will respond to climate change.

Taylor and Kumar (2014) used species distribution models (SDMs) to project the recent and future distributions of Lantana on the islands of Fiji. The researchers used phenological observations, geographical occurrence data (from both native and non-native ranges), and 5 environmental variables derived from temperature, precipitation, and relative humidity to estimate the potential distribution under historical climate (1950-2000). They then used a global climate model to project the plant’s future distribution in 2030 and 2070 under two climate scenarios.  The higher scenario (A2) corresponds to a global mean temperature increase of ~4 °C above pre-industrial by 2100, while under the midrange scenario (A1B) global average temperatures would be about 3.4 °C higher by century’s end.

Results

When using the historical data (1950-2000), the modeled distribution of Lantana was a good match to the known distribution of the plant at a regional level (Vanuatu, New Caledonia, and Solomon Islands). The model also indicated that large parts of Fiji are currently conducive to Lantana growth and spread. When the model was used to project the future distribution of Lantana, however, it indicated a contraction in the species’ range; all of Vanua Levu and western Viti Levu would remain climatically suitable for Lantana until 2030, but suitability would decrease in 2070 with only the west coast of Viti Levu and the island of Tavenui remaining at risk of Lantana invasion. This was due to projected increases in wet stress (one of the indicies modeled) due to a projected increase in soil moisture levels. These results did not depend on emission scenario (both scenarios showed similar results).

Management Considerations

• Not all species will respond the same to climate change; the distribution of some invasive species may contract in the future as shown by this example of Lantana in Fiji.
• Consider monitoring for shifts in the distribution of invasive weeds and adapt management as conditions change; an early detection and rapid response system for established invasives shifting distribution with climate change may increase effectiveness of control efforts.
• Climate change could affect how managers prioritize management; responses to declining invasive species abundance or distribution due to climate change could include 1) do nothing and monitor, 2) invest more resources in control, especially if eradication becomes possible, or 3) direct resources elsewhere, especially to control other invasive species that may be increasing due to climate change.

Take Home Points

• Species distribution models for invasive plants can be informative tools to understand invasive species distributions in the Pacific region, and projected distributions that use current and future climates may be useful to help prioritize management.
• Climate change may reduce the distribution of certain invasive weeds such as Lantana, where habitat quality for the species is expected to decline due to increases in soil moisture.
• More modeling studies of the potential future ranges of invasive plants are needed for Pacific Island jurisdictions to assist with prioritization efforts and long-term planning.