The impact of national and international policies on the spread of invasive exotic trees: A closer look
Posted on Jul 4, 2023Author(s)
Aïcha Besser
Communications Manager
CLIMACT
Expert(s)
Dr. Manoa Rajaonarivelo
FGSE, UNIL
In recent decades, nature-based solutions have received particular attention for their role in tackling the current climate change crisis. Countries rich in natural capital, such as Madagascar, with high levels of endemism, have received global recognition for the importance of their resources. Although restoration efforts have been undertaken, they have resulted in the reforestation of exotic species, leading to biological invasions and posing a threat to native biodiversity.
This interview aims to explore how national and international climate policies can influence the spread of invasive exotic trees and the implications for climate change:
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How are invasive exotic trees currently a problem for the climate?
Dr. Manoa Rajaonarivelo: Biological invasions are the second biggest threat to biodiversity. Invasive exotic trees in particular are problematic because climate change can exacerbate their spread, affecting dynamism and capacity (water availability, relationship with other species, carbon retention), reducing specific diversity and making invaded natural ecosystems vulnerable (to fire).
Can you give an example of a national or international policy linked to climate change that has helped combat the spread of invasive exotic trees, and what impact it has had?
Dr. Manoa Rajaonarivelo: None of the national or international policies linked to climate change specifically address the spread of invasive exotic trees. Nevertheless, one of the national policies on Reducing Emissions from Deforestation and Forest Degradation in Madagascar specified the need to carry out reforestation for biomass production purposes with fast-growing species outside the natural forest. This was obviously put in place to avoid the risk of invasion. Yet, in the absence of a concrete management policy to back it up, private reforestations even within forested areas have become fixed on the use of exotic species.
What measures or strategies can be implemented at policy level to mitigate the negative effects of invasive alien trees in the context of climate change?
Dr. Manoa Rajaonarivelo: First and foremost, we need to avoid or even minimize the risks of exotic tree invasion through restoration efforts as part of climate change mitigation. For this reason, in addition to efforts to increase forest cover for carbon storage, it is essential to integrate more biodiversity indicators into restoration projects.
Restoration strategies also need to diversify restoration objectives on a landscape scale in line with local needs, to make them more multifunctional, and to avoid as far as possible large-scale monoculture of exotic plants.
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