Are the changes detectable? OR What are the (important, confident, ready-to-solve) gaps in terrestrial observation systems? OR Why (and where) we need more data

In order to detect change, we must Anticipate the change Anticipate the change  Past behavior  Recent observations  Models Have the right data series or measurements Have the right data series or measurements

Why is there uncertainty? Unknown or uncertain function Unknown or uncertain function  “We need more data” Misinterpretation (trends ≠ future, nonlinearities) Misinterpretation (trends ≠ future, nonlinearities)  Move from empirical to process-based understanding Model or measurement error Model or measurement error  Model comparison, networks Surprises Surprises

Focus on vegetation as an important ecosystem integrator (as an example)

Things that we know Vegetation has changed dramatically and rapidly during the Holocene Vegetation has changed dramatically and rapidly during the Holocene Warmer temperatures lead to increased woody vegetation Warmer temperatures lead to increased woody vegetation Permafrost is linked to both vegetation and temperature Permafrost is linked to both vegetation and temperature Reindeer/caribou herds don’t do well with lots of birch in their diets (but they like Salix pulchra) Reindeer/caribou herds don’t do well with lots of birch in their diets (but they like Salix pulchra)

Things that we don’t know (not complete) Vegetation-hydrology-permafrost-snow interactions Vegetation-hydrology-permafrost-snow interactions When, where, and at what rate will vegetation change? When, where, and at what rate will vegetation change? Both role and pattern of moss cover and composition Both role and pattern of moss cover and composition Importance of changes in phenology to both ecosystem processes and ungulates Importance of changes in phenology to both ecosystem processes and ungulates Importance of slow and fast drivers Importance of slow and fast drivers

Temperature Vegetation Plant Population Internal processes (energy and nutrient capture and allocation) “Environment” (microclimate, nutrient and water pools and fluxes) X X SLOW FAST

Slow change: carbon uptake and allocation 4-6 yr0-3 yr “Effect Size” (D) Change in deciduous shrub cover: Global data set

Fast change (examples) Large-scale hydrology and permafrost changes, disappearance of ponds Large-scale hydrology and permafrost changes, disappearance of ponds Immigration of key species Immigration of key species  Ex: appearance of black spruce

RECOMMENDATIONS Focus on highly integrative aspects Focus on highly integrative aspects  Vegetation  Hydrology and permafrost Don’t stop high quality time series! Don’t stop high quality time series! Use networks and meta-analysis Use networks and meta-analysis Continue to work at (and link) multiple time and space scales Continue to work at (and link) multiple time and space scales Improve dynamic vegetation models Improve dynamic vegetation models Experiments Experiments  Sustained and whole watershed