Climate Change Unsettles Nature's Clock

Research led by the University of Oviedo has identified that climate change is currently causing species to no longer synchronise with signals from their environment. This is causing a loss of synchronisation across periodic events such as the flowering of plants, the migration of birds and the hatching of insects. For plants to flower when their pollinators are nearby, or for birds to breed when there is food for their chicks, these species need to follow the cues provided by their environment. The study - carried out in collaboration with the University of Helsinki and the Swedish University of Agricultural Sciences - addresses these periodic events that are observed in nature and are referred to as phenology. The results have been published in the journals Nature Climate Change and Proceedings of the National Academy of Sciences of America.

Researchers have meticulously gathered observations of hundreds of phenological events over decades within more than 150 protected areas throughout the region of the former Soviet Union. This huge dataset has opened up an unprecedented opportunity to explore responses to climate change over a very large area and over a very long timescale.

The results show significant local differences in the way species respond to variations from year to year. "We have information on very different phenological events for birds, mammals, amphibians, plants, reptiles, and more - ranging from the first song of the coal tit to the appearance of the common toad and the falling of birch leaves", says the study's lead author, María del Mar Delgado of the University of Oviedo's Joint Biodiversity Research Department located on the Mieres Campus. What has been observed is a general rigidity in how species respond to variations in climate from year to year.

In particular, the warmer the year, the greater the desynchronisation between phenological events and signals from the environment. In addition to this, it has been observed that there are large differences across the seasons and between sites. In the huge region of the former Soviet Union, the speed at which phenological events are changing over time depends on when the event occurs (spring or autumn), the trophic level to which the species belong (plants, herbivores or predators) and whether they are found in warm (southern) or cold (northern) locations.

Professor Tomas Roslin (from the Swedish University of Agricultural Sciences) is one of the main authors of this study and explains that the observed mismatch "is the result of different species' evolving in the past to local conditions that limit their ability to adapt to the new conditions imposed by climate change".

Roslin uses a metaphor to explain why these results are of such concern: "Have you ever played Jenga, the game where you create a tall tower of wooden blocks stacked on top of each other? Consider what would happen if, after building your tall, strong Jenga tower, you tried to move the lowest layer of blocks. With the different layers moving at slightly different speeds, your tower will first sway dangerously and then crumble. It doesn't take much imagination to replace your bricks with species stacked on top of each other... what we don't want to happen is for the whole construction to collapse. Natural communities are generally unlikely to respond to climate change as a set of disconnected species living at the same time and in the same place. Instead, they interact with each other, and this means that ecological communities tend to be prone to respond as a whole, which can make them robust in terms of the Jenga effect at local level...but only up to a point."

Over many decades, in some cases a full century, numerous scientists have been collecting data on phenological events among more than 150 protected areas in the former Soviet Union. These were meticulously compiled in an annual report, one per year and per protected area. "For a long time, this unique scientific contribution remained hidden in the archives. However. over the past decade, we have been working on mobilising this data with an amazing group of over 300 colleagues from more than 80 organisations in Russia, Ukraine, Belarus, Kyrgyzstan and Uzbekistan," explains Evgeniy Meyke of the University of Helsinki (Finland), who, together with Otso Ovaskainen from the same university, has coordinated this huge database.

This information, which has been brought together in what they have called "The Chronicles of Nature", is exceptional in many respects: it is comprehensive and covers all types of species and phenological events as well as long periods of time (almost a century), and large physical areas (half of Asia). It has been systematically gathered by scientific staff working full-time on this task.

Many of the people involved in this study have spent their entire lives collecting this data. Indeed, at the time of publication, six of them had already died. These articles are, therefore, a tribute to their work. "The project has been an exciting journey and is just the beginning," says Maria del Mar Delgado, who is joined by Professor Otso Ovaskainen: "We are enthusiastic about the high level of motivation among the professionals with whom we work on this. They give the world the opportunity to see these lifetime results, which until now have remained unknown to the international scientific community".

Articles

Delgado, M.M., [207 authors] & Ovaskainen, O. 2020. "Differences in spatial versus temporal reaction norms for spring and autumn phenological events". Proceedings of the National Academy of Sciences 2(11):1-10

Roslin, T., [207 authors] & Ovaskainen, O. 2020. "Phenological shifts of abiotic events, producers and consumers across a continent". https://www.nature.com/articles/s41558-020-00967-7