by Caitrín Farren
Medicinal plants (MP) are an invaluable resource for human health and wellbeing. They are the primary source of medicine for 80% of people in developing countries, and 25% of prescribed drugs worldwide are MP-derived (WHO, 1993; Chen et al., 2016). The popularity of MPs has grown by 8-15% annually in recent years due to global increasing population, and to a larger degree, the increasing demand for plant-based, natural medicines (Schippmann et al., 2002).
Within the Anthropocene- the current geological epoch in which human activities govern most planetary processes- is the sixth mass extinction (Gray, 2018), and it is estimated that 50,000 plant species are under threat (Willis, 2017). 15,000 of these are MP species, accounting for approximately 18-30% of flowering MP species in existence today (Chen et al., 2016). The increased demand for MPs, along with climate change, has exacerbated the pressures on MPs, and thus accelerated the loss of MP biodiversity.
The degradation and destruction of natural habitats is the largest threat faced by MPs (Hamilton, 2004; Aqbar Wani et al., 2021). This degradation of natural habitats is caused by human modification of natural areas and anthropogenic climate change (Teller et al., 2014). This destructive synergy has caused a loss of MP materials, leading to a supply-demand imbalance in the growing MP market (WHO, 1993), and culminates in an ecosystem aggravation of increased harvesting pressure, and over-exploitation of MP resources (Canter et al., 2005; Hamilton, 2004; Sharma & Thokchom, 2014). The resulting population decline of MP species leads to a loss of genetic diversity (Canter et al., 2005), resulting in reduced reproduction and survival rates, as well as limited climate resilience within populations (Frankham, 2003).
So habitat destruction, harvesting pressures, climate change and genetic erosion all contribute to the increased extinction risk that MPs currently face. Various recommendations of action have been made by WHO, IUCN, WWF (WHO, 1993) and the Convention of Biological Diversity (Secretariat of the Convention on Biological Diversity, 2020) to conserve MPs, with varying degrees of efficacy.
“The degradation and destruction of natural habitats is the largest threat faced by MPs”
The recommendations revolve around an establishment of a species inventory system with which the abundance of MP species can be monitored effectively, the implementation of sustainable harvesting practices, the development of policies and programmes to protect MP resources and the necessity for an increased effort towards in situ and ex situ conservation worldwide (Hamilton, 2004). This particular article above reviews the suitability and effectiveness of selected ex situ and in situ conservation methodologies for MPs worldwide, setting the basal criteria for future research and practice to assess and implement the best approaches to prevent MP species from endangerment and extinction.
Protected areas and natural reserves have increased by 42% in the last decade, and as of May 2021, approximately 22.5 million km2 of land and inland ecosystems are protected (Nacions, 2020). Protected areas prevent the loss of medicinal plant resources by prohibiting the degradation and destruction of their natural habitats (Chen et al., 2016; WHO, 1993). These protected natural reserves play a significant role in the preservation of MP resources and MP biodiversity (Aqbar Wani et al., 2021; Hamilton, 2004, Chen et al., 2016), by inhibiting the aforementioned pressures of genetic erosion (Bellon et al., 2017) and overharvesting/exploitation.
“Protected areas and natural reserves have increased by 42% in the last decade, and as of May 2021, approximately 22.5 million km2 of land and inland ecosystems are protected”
However, much of the research in support of protected areas and reserves fail to consider the evolving pressures associated with changing earth system and biotic responses in the Anthropocene that compromise the conservational ability of these areas (Chen et al., 2016; WHO, 1993)
Human activities and climate change can vastly reduce the functionality of protected areas, which were not designed to respond to current rate of earth system change (Heywood, 2019). It is estimated that 32.8% of protected areas globally are majorly threatened by land use change (Jones et al., 2018). As land is cleared there is the risk that existing natural reserves will shrink. Additionally, rising temperatures are causing plants to shift their habitable ranges polewards, to higher elevations and higher latitudes, into more suitable habitats (Pecl et al., 2017). These more suitable habitats may occur outside of existing static protected areas, meaning that MP species could suffer population decline and face extinction (Heywood, 2019).
“rising temperatures are causing plants to shift their habitable ranges polewards, to higher elevations and higher latitudes, into more suitable habitats”
The same fate may meet some MP species which may not be able to redistribute due to a physical limit to their range, lack of natural corridors, or otherwise (Rodríguez et al., 2007). Plant species redistribute at an average of 16km per decade (Chen et al., 2011), a speed slower than the rate of change in the environment around them (Bertrand et al., 2011) meaning that MP population decline is inevitable, even in protected areas. Such barriers create opportunities in the use of ex situ conservational techniques to protect MPs from endangerment, such as seed banks and botanic gardens.
Although there are many disadvantages to protected areas and reserves, in situ conservation remains the most successful method of conserving biodiversity presently as it considers a whole ecosystem conservation approach compared to an ex situ approach of protecting species with less thought of biotic interrelations. Thus, in situ conservation methods increases the success rate of stewarding biodiversity (Forest et al., 2007) and by doing this, they maintain the diverse genetic material needed for MP species to evolve to the selective forces of the Anthropocene (Bellon et al., 2017).
Evergreen Trinity 