Ilkka Hanski (1953–2016) Population Ecologist Who Modelled How Species Cope with Habitat Loss

COMMENT OBITUARY Ilkka Hanski (1953–2016) Population ecologist who modelled how species cope with habitat loss.

cologist Ilkka Hanski’s pioneering In 2003, nearly 25 years after completing work changed our understanding his thesis, Hanski returned to his beloved of how biodiversity is maintained. dung beetles. He launched a project in ECombining mathematical modelling and Madagascar to study the evolutionary biol- long-term data from the wild, he developed ogy of the island’s diverse endemic species MARCETIC MARKUS metapopulation theory. This predicts the of dung beetle and how these ecologically degree of habitat fragmentation beyond crucial communities respond to habitat loss. which a species will go extinct. He led a series of excursions to Madagascar Hanski’s 1999 book Metapopulation to work with local students, his team from Ecology (Oxford University Press) became Finland and his family. These trips became a cornerstone for researchers in population legendary, both for their scientific value and biology, conservation biology and landscape for the camaraderie he fostered. ecology. He identified the genetic basis of Among numerous honours, Hanski was traits that underpin survival in fragmented awarded ecology’s top gong, the Crafoord habitats. Most recently, he demonstrated with Prize in Biosciences, in 2011. And despite colleagues that an increasing prevalence of his hectic schedule, he always prioritized inflammatory diseases is associated with public engagement. In Finland, Hanski declining biodiversity. was known for his views on conservation, Hanski, who died on 10 May, was born in in particular the protection of old-growth 1953 in Lempäälä, Finland. As a child he col- to choose the Glanville fritillary butterfly forests. Hanski was also a powerful advocate lected butterflies at his grandparents’ house in (Melitaea cinxia) in the Åland Islands off for basic research, criticizing science policy southeastern Finland. Decades later, Hanski southern Finland to test his predictions. that demanded immediate economic ben- reflected that many of his most successful In the early 1990s, he set out to map all efit and arguing that such short-sighted aims research projects were inspired by these out- suitable habitat patches for M. cinxia in threaten the fundamental process by which door adventures and by the encouragement Åland. His effort has grown into a database knowledge is generated. that he received from Esko Suomalainen, a of more than 4,000 localities. These places Training young scientists was a top prior- geneticist at the University of Helsinki whom are checked each year for M. cinxia and its ity. Always keen to discuss ideas and offer he had contacted after finding a rare butterfly larval host plants — as well as the parasitoids feedback on manuscripts, Hanski became a at his grandparents’ house. and pathogens of each. co-author only on papers on which he felt Hanski studied biology at the University This has since become one of the most he had made a significant intellectual con- of Helsinki and gained his doctorate, on important model systems in population tribution. This policy promoted the inde- the community ecology of dung beetles, biology. A one-of-a-kind long-term data- pendence of early-career scientists working from the University of Oxford in 1979. He collection effort, it is revealing how species in the Metapopulation Research Centre. He found that most dung-beetle species clump and their interactions are responding to cli- loved to debate, and challenged everyone — together, with particular species common mate change, as well as shedding light on how regardless of their career stage — to discuss in some pats but scarce or absent in others. species cope with habitat fragmentation. topics ranging from science to society. Before the 1970s, ecologists paid little atten- In 1994, Hanski published the incidence- Ilkka lived in Helsinki with his wife Eeva tion to whether populations were distributed function model, which elegantly formulated Furman, a professor of environmental policy, continuously or in many local patches or both. the relationships between the area and isola- and three children. He was dedicated to his Throughout his career, Hanski was intrigued tion of a habitat patch and the likelihood of it family, a quality that resulted in a family- by the ecology and evolution of species found being occupied by a species (I. Hanski J. Anim. friendly working environment in the centre. in islands — naturally fragmented habitats. Ecol. 63, 151–162; 1994). This launched a new After being diagnosed with cancer in 2014, In 1969, population biologist Richard Levins era of spatially explicit population models and Ilkka, with typical determination, completed introduced the concept of a metapopulation was quickly adopted by ecologists. projects closest to his heart — notably a book, — a ‘population of populations’ — species Those of us who worked with Hanski will Messages from Islands: A Global Biodiversity living in networks of habitat patches such as remember his sharp intellect and ceaseless Tour, to be published in December. cowpats or islands, work that Hanski built on. enthusiasm for understanding nature. He was Ilkka had so much more to give and he Returning to Helsinki after his doctor- quick to adapt new methods and techniques. touched so many in the ecology community. ate, Hanski continued to develop models for The Metapopulation Research Centre in Hel- His death leaves a gap that won’t be filled. ■ metapopulation survival. By the late 1980s, he sinki that Hanski established in 2000 consists was ready to test his predictions in the field, of ecologists, evolutionary biologists, math- Anna-Liisa Laine is professor of plant but which insect to study, and where? He was ematicians, bioinformaticians and molecu- ecology at the University of Helsinki, inspired during a fortuitous visit by renowned lar biologists. Hanski also led Finland’s first Finland. Ilkka Hanski supervised her PhD population biologist Paul Ehrlich of Stanford sequencing of an animal or plant genome: between 2001 and 2005, and she joined the University in California. Discussions about that of his Glanville butterfly, published in Metapopulation Research Centre as a group Ehrlich’s research on Edith’s checkerspot but- 2014 (V. Ahola et al. Nature Commun. 5, leader in 2010. terfly (Euphydryas editha) prompted Hanski 4737; 2014). e-mail: [email protected]