30 years of climate related phenological research: themes and trends.

Anthropogenic climate change has caused changes in the seasonal timing (phenology) of life-cycle events with consequential impacts on ecosystem functioning and biodiversity. Over the last 30 years, climate-related phenological research has expanded rapidly. To identify key themes and knowledge gaps in this research landscape we used a text-based analysis approach, topic modelling. Our systematic literature search identified 4,681 publications on phenology between 1989 and 2019. We showed taxonomic and geographic bias in the literature with a large proportion of publications on bird migration and reproduction, insect phenology, marine phenology, and agriculture, focused within the Northern hemisphere. Our results reflected the decadal advances in technology, for example remote sensing studies increased the most in popularity. Topics related to genetics increased along with mismatching, which has impacts on species fitness. While climate-based topics were highly connected, there was little connectivity between different disciplines and newer areas of research. Remote sensing rarely co-occurred with other topics, insect phenology was either being studied with plants or birds instead of being considered as part of a network, and mismatching was rarely studied alongside other methodologies in phenological research. We suggest that transdisciplinary research considering species as part of a system and analyzing new or understudied taxa and regions should be prioritized. The disjuncts identified in this analysis inhibit development of a coherent view of the impact of phenological changes on biodiversity and will have implications for conservation management.