Distributions of Alien Invasive Weeds under Climate Change Scenarios in Mountainous Bhutan

Abstract

Climate change is viewed as a cause in accelerating the rate of invasion by alien species in addition to the globalization of anthropogenic activities. Ecological niche modeling has become an instrument in predicting invasion from natural or invaded ranges to uninvaded ranges based on the presence records of organisms and environmental parameters. This study explored the changes in the distributions of globally noxious alien species (Aegratina adenophora, Ageratum conyzoides, Chromolaena odorata, Lantana camara, Mikania micrantha, and Parthenium hysterophorus) in Bhutan, to provide evidence that even a mountain environment is under the threat of invasion given the change in climatic conditions. With fairly high accuracy, the model results suggest that there will be a potential increase in the areas of invasion among most of the species, except Parthenium hysterophorus, which will experience a northerly shift and decline in distribution. The results also indicate changes in patterns of invasion, some becoming more concentrated toward a given direction, while others become more dispersed over time. This study provides a framework that can be used in the strategic control of the species, future detection surveys, and further research.Agronomy 2019, 9, 442 2 of 16 recreational amenities for ecotourism, deforestation, and upland agriculture adoption [19], compounded by climatic change, have exposed vulnerable mountains to disturbance [20][21][22][23][24]. The warming climate has resulted in an altitudinal upward shifting of cold-temperate species (e.g., Fagus sylvatica) and Mediterranean species (Quercus ilex) in Catalina, Spain [25]. In Bhutan, farmers have reported that due to climate change, invasive plants have started to colonize highland pasture, preventing the regeneration of fodder grasses [26]. Given a change in climatic conditions, adjacent lowland flora heavily influence species composition in mountain communities [27]. Mountain environments are rated as highly sensitive to climate change due to a short growing season and limited niches for resident species [28][29][30][31][32]. Human activities and climate change has led to invasions in mountainous areas in Europe, Australia, South Africa, Kashmir, Hawaii, the United States Pacific Northwest, and Chile [20]. Furthermore, alien invasive weeds are habitat generalists, with high plasticity to adapt to wide ranges of climatic conditions [33][34][35][36][37]. Species tolerant of wider environmental conditions are frequently associated with the following physiological traits: an efficient use of nutrients in low nutrient soils, higher root-shoot ratio in arid systems and a lower root-shoot ratio in light-limited systems for resource acquisition, lower leaf construction costs and higher photosynthetic energy use efficiency as well as early phenology in arid systems [38,39].With its inhospitable terrain and strong conservation strategies (maintaining 60% or more forest cover, with more than 51% designated as protected areas and with a rigid forest management rule...

Predicting the distribution of parthenium weed (Parthenium hysterophorus) under current and future climatic conditions in Bhutan

“…Yet, species distribution modelling has never been used, especially in spatial planning and decision-making in the context of plant invasion. Thinley et al (2019) tried to model six alien invasive species, including parthenium weed in Bhutan using the most commonly implemented MaxEnt tool (Santini et al 2021). However, the study did not provide appropriate details in terms of districts suitability and elevational changes other than range expansion, contraction, and directional change, which have limited use when planning for management programs.…”

“…Other than the study conducted by Thinley et al (2019) and Chhogyel et al (2021), no study had been conducted on IAPS distribution in Bhutan. Both the studies implemented the most commonly used species distribution modelling program (-MaxEnt ) (Santini et al 2021) and provided a general overview of parthenium weed distribution at the national level and West-Central region, respectively under current and a future climate (predicted for 2070).…”

“…Bhutan, a tiny Himalayan democratic constitutional monarchy with an area of 38, 394 km 2 , a population of about 0.72 million (SYB 2020) endowed with very rich biodiversity (Gyeltshen et al 2019) is no exception and considered spared from invasion by IAS. There are already a number of IAS reported in Bhutan (Dorjee et al 2020;Mahat et al 2021;Thinley et al 2019;Tshering and Adkins 2012;Wangdi 2015;Weiss et al 2004;Yangzom et al 2018), including Crofton weed (Ageretina adenophora (Spreng.) King & H.Rob.…”

Predicting the Current and Future Distribution of the Invasive Weed Ageratina adenophora in the Chitwan–Annapurna Landscape, Nepal

“…Studies in other parts of the world have also predicted the expansion of climatically suitable areas for A. adenophora in future climate scenarios (Wang and Wang 2006;Zhu et al 2007;Wang et al 2017;Lamsal et al 2018;Thapa et al 2018). However, a study conducted in Bhutan predicted a contraction of suitable areas for A. adenophora by 0.22% in 2050 (Thiney et al 2019). An experimental warming study conducted in China revealed that warming (28C rise) increased biomass allocation and canopy cover of the weed, making it more stress tolerant (He et al 2012).…”

Predicting invasion potential of Senna didymobotrya (Fresen.) Irwin & Barneby under the changing climate in Africa

“…Climate change has a profound effect on the introduction and establishment of invasive species (Roura-Pascual et al 2011). Climate warming could facilitate the dispersal and performance of invasive alien species, which would allow range expansion and new invasions (Thiney et al 2019;Walther et al 2009). Moreover, climate change facilitates the distribution of alien species into new areas through removing constraints to species dispersal and survival such as temperature or moisture (Hellmann et al 2008;Mainka and Howard 2010).…”