What is palaeoecology and why is it important?

• Historical climate records usually only go back about 200 years - if we want to know more than that we need paleo records

What is palaeocology

• A multidisciplinary field studying interactions between organisms and their envirnments using palaeoenvironmental archives (physical, chemical and biological properties)
• Combining different methods to learn about the past
• More or less the only tool to go beyond the time scales of direct measurements to learn about past environments
  • Works for both regional and global (climate) trends

What kind of archives of environmental history exist?

Glaciers/ice sheets

• A bit challenging because they are always moving
• They trap air bubbles within them where we can measure gas concentrations through ice cores
• Also ash, pollen grains

Coral reefs

• Calcaerous animals take carbon dioxide and other gases from the atmosphere over different layers

Speleothems (stalagmites)

• The calcium carbonate can be analyzed for gas concentrations

Tree rings (dendrochronology)

• Determine growth rate in different years, also chemical composition in the different rings
• Annual resolution

But the three most important for this course are:

Environmental Archives - Oceans

• Oceanic sediment

Environment Archives - Lakes

• Pollen and diatoms from lake sediments
• At Kilpisjärvi they once found some perch scales from 9000 years ago but this is very rare (they sent it to Luomus for archiving)

Environment Archives - Peatlands

• Plant macrofossils, amoeba, pollen, twigs gives an idea of vegetation surrounding the peatland

Importance of paleoecology

Example - pH of lake in Nuuksio

• If you look at instrumental records going back to the 1930s, it looks like the lake is quickly acidifying
• If you look at paleorecords going back to 1900, it was similar pH at this time, then got more basic and now is trending back to what it was
• If you go back 10 000 years, its generally stayed pretty consistent since glaciation

Example - diatom group analysis of lake in Sweden (1986)

• used hundreds of samples and grouped diatoms into groups based on pH preferences, then inferred pH based ontheir relative frequencies
• Shows a trend of slow acidification 12000 - 8000 a, then reduction in acifification with first human settlemenets 2300 bp, then rapid acidification beginning 1900

Example - drought dynamics in western USA (2004)

• moisture reconstruction from tree ring data going back 2000 years
• Was slowly getting wetter before around 1915 and then suddenly dryer
• It's important to look really far back to establish a baseline trend for drought management

Important terms

Autochthonous

• Coming from the same place

Allochthonous

• Originated from somewhere else

Proxy

• Indirect source of information e.g. using pollen concentrations as a proxy for mean temperature

Core

• A cylinder of sediment, ice, wood used to study past climate proxies

Stratigraphy

• Studying how layers of sediment overlap and interact

Transfer function

• Mathematical model to infer data from present to past

Subfossil

• weakly fossilized, relatively young remain of biota

Holocene

• The last 10 000 years more or less, our current era
• In northern europe, the time where the last glaciation was ending

Anthropocene

• A proposed epoch where human impact on environment is significant
• Debate on when the beginning is - 200 years or 8000 years (rice cultivation)?
• We need a definitive record in sediments to determine the start of an epoch

Taphonomy

• The study of how organisms decay and become fossilized
• Important for determining why some organisms fossilize and others don't

Recent developments in paleoecology

Quantitative approaches

• in the last few decades, due to computer power, a lot more multivariate statistical analyses and modeling is used in palaeoecology

Careful planning and execution of research

• Planning research and taking all variables into account is becoming more important
• Creating testable hypotheses and critically analyzing data

Taxonomic accuracy

• More resources and standardization of techniques, scanning electron microscopes, has allowed researchers to get better at identifying fossils precisely
• Also resulted in lots of taxa being split

Spatial coverage

• Expanding data to a global perspective - big datasets published online free for anyone to use
• It used to be that applications were all pretty local, based around one lake, now that the data is more available it can be used for regional / global applications