Tutkimuksen ja opetuksen kuvaus

RESEARCH

My research team focus on four main topics: 1) Impacts of climate change on Arctic vegetation, ground-surface conditions and biodiversity, 2) Remote sensing and GIS in spatial modelling, 3) Modelling of earth surface processes and 4) Machine learning in palaeoclimatology.

Impacts of climate change on Arctic vegetation, ground-surface conditions and biodiversity

High-latitudes are undergoing rapid and significant change associated with climate warming. This puts global change research at the centre of the international scientific agenda. This project will 1) investigate dynamics and the main drivers of recent changes in the Arctic vegetation; 2) threats caused by climate change to Arctic plant diversity, 3) develop projections of the changes in the Arctic plant biomass patterns under future climates, 4) forecast the geomorphic sensitivity of the Arctic throughout the 21st Century, and 5) identify threat spots of Arctic infrastructures in the face of climate warming. This project is part of two research consortiums funded by the Academy of Finland: a) Impacts of climate change on Arctic environment, ecosystem services and society (Finnish Research Programme on Climate Change) and Geomorphic Sensitivity of the Arctic Region: Geohazards and Infrastructure (Arctic Academy Programme).

Remote sensing and GIS in biodiversity modelling

Remote sensing (RS) produces valuable information for biodiversity mapping and monitoring. Due to high spatial and temporal coverage, RS data have clear advantages compared to any other source of information. We develop novel approaches to integrate RS and geographic information (GI) data into biodiversity assessments. Our ultimate goal is to provide information which is directly applicable in defining biodiversity assessment practices that better meet the requirements of the sustainable use of natural resources and land use planning. Funded by the Academy of Finland.

Spatial modelling of periglacial processes

Determination of the environmental factors controlling earth surface processes and landform patterns in cold regions is one of the central themes in periglacial geomorphology. We focus on the spatial modelling of periglacial processes under the global change. Additionally, we investigate and develop novel spatial approaches in predictive geomorphic mapping.

Machine learning in palaeoclimatology: increasing the sensitivity and robustness of climatic reconstructions

With proceeding anthropogenic climate change there is a growing need to understand the long-term natural variability of climate in order to predict future climatic developments and their
consequences. Palaeoclimatic data based on biological fossils preserved in sediments are one of the most important sources of information on past climatic variability. This project seeks to find new and improved ways to study past climate changes with novel machine-learning methods, based on application of artificial-intelligence algorithms. With these techniques there is great
potential to increase the reliability of estimates on past climatic conditions, which is of utmost importance in the assessment of modern climatic change. In addition, the project applies these
new methods in practice, by studying Northern European climate development based on a rare sediment sequence from Finnish Lapland, extending through and beyond the last ice age (i.e.,
covering the past 130 thousand years).

SCIENCE HIGHLIGHTS

Here I will present highlights of the recent research projects. Requests for materials should be addressed to firstname.lastname[at]helsinki.fi.

Human population dynamics in Europe over the Last Glacial Maximum                    Proceedings of the National Academy of Sciences 2015, 112, 8232-8237.

doi:10.1073/pnas.1503784112                                                                               

Tallavaaraa, M., Luoto, M. , Korhonen, N., Järvinen, H., & Seppä, H. 

Abstract

The severe cooling and the expansion of the ice sheets during the Last Glacial Maximum (LGM), 27,000–19,000 y ago (27–19 ky ago) had a major impact on plant and animal populations, including humans. Changes in human population size and range have affected our genetic evolution, and recent modeling efforts have reaffirmed the importance of population dynamics in cultural and linguistic evolution, as well. However, in the absence of historical records, estimating past population levels has remained difficult. Here we show that it is possible to model spatially explicit human population dynamics from the pre-LGM at 30 ky ago through the LGM to the Late Glacial in Europe by using climate envelope modeling tools and modern ethnographic datasets to construct a population calibration model. The simulated range and size of the human population correspond significantly with spatiotemporal patterns in the archaeological data, suggesting that climate was a major driver of population dynamics 30–13 ky ago. The simulated population size declined from about 330,000 people at 30 ky ago to a minimum of 130,000 people at 23 ky ago. The Late Glacial population growth was fastest during Greenland interstadial 1, and by 13 ky ago, therewere almost 410,000 people in Europe. Even during the coldest part of the LGM, the climatically suitable area for human habitation remained unfragmented and covered 36% of Europe.

Potential for extreme loss in high-latitude Earth surface processes due to climate change Geophysical Research Letters 2014, 41, 3914–3924.                                                          doi: 10.1002/2014GL060095                                                                                       Aalto, J., Venäläinen, A., Heikkinen, R.K. & Luoto, M. 

Abstract

Climatically driven Earth surface processes (ESPs) govern landscape and ecosystem dynamics in
high-latitude regions. However, climate change is expected to alter ESP activity at yet uncertain rate and amplitude. We examined the sensitivity of key ESPs (cryoturbation, solifluction, nivation, and palsa mires) to changing climate by modeling their distribution in regard to climate, local topography, and soil variables in northern Fennoscandia. The distributions of ESPs were then forecasted under two future time periods, 2040–2069 and 2070–2099, using ensemble modeling and three emission scenarios. Increase of 2°C in current temperature conditions caused an almost complete loss of ESPs, highlighting the extreme climatic sensitivity of high-latitude geomorphic processes. Forecasts based on three scenarios suggest a disappearance of suitable climate for studied ESPs by the end of this century. This could initiate multiple opposing feedback between land surface and atmosphere through changes in albedo, heat fluxes, and biogeochemical cycles.                                                                                       

Recent vegetation changes in the high-latitude tree-line ecotone are controlled by geomorphologic disturbance, productivity and diversity
Global Ecology and Biogeography 2010, 19, 810-821.
doi:10.1111/j.1466-8238.2010.00570.x
Virtanen, R., Luoto, M., Rämä, T., Mikkola, K., Hjort, J.; Grytnes, J-A., & Birks, J.

Abstract                                                                                                              
Aim We test how productivity, disturbance rate, plant functional composition and species richness gradients control changes in the composition of high-latitude vegetation during recent climatic warming.                                                                               
Location Northern Fennoscandia, Europe.                                                        
Methods We resampled tree line ecotone vegetation sites sampled 26 years earlier. To quantify compositional changes, we used generalized linear models to test relationships between compositional changes and environmental gradients.                               
Results Compositional changes in species abundances are positively related to the normalized difference vegetation index (NDVI)-based estimate of productivity gradient and to geomorphological disturbance. Competitive species in fertile sites show the greatest changes in abundance, opposed to negligible changes in infertile sites. Change in species richness is negatively related to initial richness, whereas geomorphological disturbance has positive effects on change in richness. Few lowland species have moved towards higher elevations.                                                                                                         
Main conclusions The sensitivity of vegetation to climate change depends on a complex interplay between productivity, physical and biotic disturbances, plant functional composition and richness. Our results suggest that vegetation on productive sites, such as herb-rich deciduous forests at low altitudes, is more sensitive to climate warming than alpine tundra vegetation where grazing may have strong buffering effects. Geomorphological disturbance promotes vegetation change under climatic warming, whereas high diversity has a stabilizing effect.

Species traits explain recent range shifts of Finnish butterflies
Global Change Biology 2009 Volume 15 Issue 3, Pages 732 – 743.
doi: 10.1111/j.1365-2486.2008.01789.x
J. Pöyry, M. Luoto, R. K. Heikkinen, M. Kuussaari and K. Saarinen

Abstract
This study provides a novel systematic comparative analysis of the species characteristics affecting the range margin shifts in butterflies towards higher latitudes, while taking phylogenetic relatedness among species into account. We related observed changes in the northern range margins of 48 butterfly species in Finland between two time periods (1992–1996 and 2000–2004) to 11 species traits. Species with positive records in at least ten 10 km × 10 km grid squares (in the Finnish National Butterfly Recording Scheme, NAFI) in both periods were included in the study. When corrected for range size change, the 48 butterfly species had shifted their range margins northwards on average by 59.9 km between the study periods, with maximum shifts of over 300 km for three species. This rate of range shifts exceeds all previously reported records worldwide. Our findings may be explained by two factors: the study region is situated in higher latitudes than in most previous studies and it focuses on the period of most prominent warming during the last 10–15 years. Several species traits exhibited a significant univariate relationship with the range margin shift according to generalized estimation equations (GEE) taking into account the phylogenetic relatedness among species. Nonthreatened butterflies had on average expanded their ranges strongly northwards (84.5 km), whereas the distributions of threatened species were stationary (−2.1 km). Hierarchical partitioning (HP) analysis indicated that mobile butterflies living in forest edges and using woody plants as their larval hosts exhibited largest range shifts towards the north. Thus, habitat availability and dispersal capacity of butterfly species are likely to determine whether they will be successful in shifting their ranges in response to the warming climate.