Botanic Gardens Conservation International
BGCI provides a global voice for all botanic gardens, championing and celebrating their inspiring work. We are the world's largest plant conservation network, open to all. Join us in helping to save the world's threatened plants.

The assisted migration debate – botanic gardens to the rescue?

Volume 9 Number 1 - January 2012

Maria Hällfors, Elina Vaara & Susanna Lehvävirta


Climate change is having a considerable impact on wild plant species, with declines in populations and distributions shifts towards the poles and higher elevations being reported by scientists. One of the most alarming estimates paints a grim picture of more than half of the European flora becoming endangered by the year 2080 due to climate change (Thuiller et al., 2005).  However, it is not only biodiversity that is experiencing the pressures brought about by such changes. Conservation actors, including botanic gardens, are being forced to re-evaluate the suitability and effectiveness of their conservation approaches and may need to consider novel strategies.

With the combined effects of climate change and habitat degradation taking its toll on biodiversity, it seems that we can no longer focus on trying to reverse the trends. Instead, we need to start working to mitigate the negative effects.  In Europe, for example, the progression of climate change will mean that more than half of the species in existing protected areas will be subject to unfavourable conditions (Araujo et al., 2011). Thus, we need to become more proactive in species conservation. Perhaps the most controversial proposal thus far is moving species beyond their historic natural ranges, a strategy often called assisted migration, assisted colonization or managed relocation. Botanic gardens, with their expertise and resources, could play an important role in investigating the possibilities of carrying out assisted migration in a sustainable way.

In this article, we aim to highlight the responsibility, skills and opportunities that BGs have in this emerging field. We will briefly review the basic ideas behind assisted migration and describe a multi-disciplinary research project that was initiated at the Botany Unit of the Finnish Museum of Natural History in 2011.

Assisted migration challenges the traditional conservation view

When the environment changes a species has two options. It can adapt or it can move to more favourable areas. Species that do not manage to do either will go extinct. We may not be able to help species adapt to new habitat requirements nor can we entirely rely on conventional conservation methods like in situ conservation in protected areas to accommodate species in a changing world. However, we could adapt our thinking and conservation strategies to find new ways to save biodiversity. Ex situ conservation offers a valuable tool for preserving threatened species (Pritchard & Harrop, 2010). Although on its own it is not a sustainable solution for conservation, it does provide an essential step in the process of introducing species back into the wild.  This could include introducing species into habitats outside their natural range, if their original habitat is no longer climatically suitable – assisted migration.

Active discussions on assisted migration have been taking place since around 2005.  Moving species to novel areas raises not only ecological, but also judicial, ethical and economical challenges. Which species should we move and when? How can we ensure that the species do not become invasive? How much should we interfere with nature, and is it even legal? And finally, how much would this cost? It is essential to develop joint research programmes that include ecological, legal, and ethical perspectives in the investigation of assisted migration.

Plant conservation prohibited by law

Currently there are few laws that unambiguously regulate assisted migration as a conservation strategy. There are, however, many legal restrictions on the movement of species in both domestic and international laws. Some of these laws restrict the intentional movement of the species itself, while others are designated to protect the areas to which species may be transferred. In an era of climate change, when assisted migration may need to be considered, these regulations may actually hinder the conservation of the world’s biodiversity, although their original intent was to enable it.

The majority of current international nature conservation treaties (e.g., Convention on Biological Diversity, Convention on International Trade in Endangered Species) were developed before a broad understanding of the impacts of climate change on species conservation had been reached. Therefore, research findings and new methods developed concerning assisted migration may require a re-consideration of current conservation legislation.  Indeed, completely new comprehensive regulation mechanisms may need to be developed. This would help to ensure that each assisted migration intervention and trial is duly coordinated and safely implemented.  However, it must also be recognised that ecological circumstances, such as climatic conditions and the level of habitat fragmentation, vary between nations. Hence, species conservation regulations which suits one nation, may not be suitable for another.

Besides the need to inform the scientific and conservation communities, professionally produced educational materials and expert advice for the public and local decision-makers are important. Already at least one case of assisted migration, uncontrolled by the authorities, has been initiated, as the “Torreya Guardians” continue to move the threatened Torreya taxifolia further north in the USA. 

 Botanic gardens have invaluable expertise and experience

Botanic gardens have a long tradition of growing plants in locations beyond their natural distribution. Thus they have ample experience to investigate the effect of macroclimatic factors on species.  Translocation trials conducted under controlled conditions can offer valuable information on the possibilities of moving species to new locations.

Botanic gardens are also lead players in the field of ex situ conservation and species reintroduction. While living collections provide experience of species requirements, all kinds of ex situ collections may offer an important source of knowledge and plant material for both the research and practical actions required for assisted migration projects. This is especially true for species that are extinct or extremely rare.

Moreover, being highly involved in invasive species management, botanic gardens also hold knowledge and share information on invasion biology, a key question to be addressed when considering moving species to novel areas. Furthermore, apart from offering valuable information for evaluating species’ current and future climatic ranges, herbarium records along with species distribution databases can also be used to predict invasion risks (Aikio et al., 2009).

New openings for botanic garden conservation - the Helsinki example
The Assisted Migration research project at the Botany Unit of the Finnish Museum of Natural History started in 2011 with an analysis of the legal and ecological aspects. To begin with, a conceptual analysis is necessary, as the debate and the terminology are still evolving. The first translocation trial between botanic gardens has been started and an assessment of the need for assisted migration in the conservation of Finnish species is underway.

The key question in the analysis of the regulations that concern assisted migration is whether we need new guidelines to enable its execution. The regulations should be compatible with nature conservation legislation at large, but also fair and just within society. Through comparing the results of the legislative analysis with current ecological knowledge, we will recognise the best model for regulation of assisted migration and present it for introduction into the Finnish legal order.

The invasive species problem and ethical questions are next in line, and in the near future we hope to be looking into aspects of population genetics, economics, and the social acceptability of using assisted migration as a conservation strategy. The uniqueness of the project lies in the multi-disciplinary approach that allows a wide-angled examination of the problem. We will also cooperate with other institutions involved in conservation in order to include the knowledge held by these organisations.

Translocation trial of Siberian primrose

The most southern variety of the threatened Siberian primrose (Primula nutans var. jokelae) grows on the shores of the Bothnian Bay. Climate change may threaten this species and the next more northern suitable habitat for this variety may be by the shores of the Arctic Sea, 500 km north of its current range. Thus, the variety may need to be assisted in its migration when climate changes.

In a translocation experiment we are studying the success of the species at three climatically different sites: the University of Oulu Botanic Garden, Finland; University of Helsinki Botanic Garden, Finland; and Svanhovd Botanic Garden, Norway. Through the trial we can compare the effect that climate in these three areas has on the Siberian primrose and find out whether macroclimatic factors are decisive for the viability of the species. From this we can extrapolate whether the southern variety could already grow on the shores of the Arctic Sea and whether a warmer climate affects it negatively. The experiment, conducted with the help of the botanic garden network will thus give us insights into the need and possibilities for assisting the Siberian primrose in its migration under a changing climate.

Multiple roles for botanic gardens in the development of assisted migration

With the rapidly emerging need for a better understanding of assisted migration, botanic gardens now have an opportunity to provide society with unique expertise. Botanic gardens can, for example, collect and disseminate information about the criteria and best practices concerning assisted migration; give expert advice concerning the ecological requirements of focal species; provide plant material and develop seed and ex situ collections to support the study and application of assisted migration; offer testing grounds for species’ reactions to different climatic conditions; and evaluate risks of invasiveness. Furthermore, the international network of botanic gardens can prove essential, as future (assisted) migration routes do not necessarily respect national borders. Hence, international assisted migration research initiatives would provide a strong platform for external funding.

Botanic gardens also routinely communicate information through their networks and public education programmes and the idea of assisted migration could be disseminated in various ways. As an example, the University of Helsinki participates in the Helsinki World Design Capital Year 2012 and the assisted migration research project is part of the University’s contribution to designing the future through scientific innovation. Together with other research initiatives concerned with climate change, we will unite recent research results with art to create discussion within both the scientific and the public community. One attempt is a science and environmental art workshop for university students, called Reclaimed Territories that will be organised in Kumpula Botanic Garden in spring 2012. The course culminates in an art exhibition that will be displayed during the summer. 
As botanic gardens are institutions connecting research, conservation, and education they are well suited for innovative research openings bringing together stakeholders, knowledge producers, and end-users from various disciplines as well as society at large. In this role of linking different sectors, they can play an important role in enhancing the debate on controversial subjects, such as assisted migration, and push the boundaries of their traditional fields of expertise.


Aikio S., Duncan, R.P. and Hulme, P.E.2009: Lag-phases in alien plant invasions: separating the facts from the artefacts. Oikos 119: 370-378

Araujo, M.B., Alagador, D., Cabeza, M., Nogues-Bravo, D. and Thuiller, W. 2011: Climate change threatens European conservation areas. Ecology Letters 14: 484-492.

Pritchard, D. J. and Harrop S. R. 2010. A re-evaluation of the role of ex situ conservation in the face of climate change. BGjournal 7(1).

Thuiller ,W.,Lavorel,S.,Araujo,M.P.,Sykes,M.T. and Prentice,I.C..2005: Climate change threats to plant diversity in Europe. PNAS 102: 8245-8250.

Maria Hallfors, Elina Vaara & Susanna Lehvavirta
Botany Unit
Finnish Museum of Natural History
P.O. Box 44(Jyrangontie 2)
FI-00014 University of Helsinki