OPINION: Paleoclimate research necessary for landscape management

The present is the key to the past is a common dictum in the earth sciences that tells us that the physical processes operating today are the same ones operating millions of years ago. While this statement has a clear retrodictive slant to it, it makes the important recognition that past and present processes, and their associated events, are essentially analogues for each other. It is not a considerable leap of logic to, therefore, assume that events that unfold in the future will be similar to events occurring today and, more importantly, to events that occurred in the past given similar environmental constraints.

This linkage between past and future events is critical in the purview of expected climatic changes, which potentially Paleoclimate Researchhave a considerable control over the state of our landscape, specifically our water resources. Much fanfare has been made in the media about the possibility of more extreme events occurring globally, but the sensitivity and response of the landscape to climatic changes, which differ regionally, haven’t yet been clearly elucidated. For instance, should temperature and/or precipitation patterns change, what sort of response could we expect from our water resources based on historic and pre-historic patterns? Will lake levels decrease or increase? If so, by how much? Can we expect greater magnitude floods or will drought conditions prevail? The important point here is that we cannot reasonably understand how our water resources, and the landscape in general, will respond to future climatic perturbations and how best to adjust management policies if we do not know how they have responded in the past.

The instrument record in southern Ontario provides data for the last 50-150 years, which only yields a very small window into our region’s climatic history. While the instrument record can offer valuable insights into annual and decadal fluctuations (i.e. low-amplitude, high-frequency variability) over the last hundred years, centennial and millennial time-scales are needed to resolve high-amplitude, low-frequency climatic changes, like those suggested by climate models, which can only be derived from proxy data in the paleorecord.

Existing paleo research on water resource response to millennial climatic variability in southern Ontario has been minimal, being largely restricted to site-specific studies. The existing work, however, does show us that lake levels within the region are fairly sensitive to high-amplitude climate change. For instance, 9,000 years ago, Lake Erie was approximately 19 metres below present levels while Lake Ontario was 64 metres below present levels 10,000 years ago. Further, it is well documented from several lakes and wetlands in south-western and south-central Ontario that a more recent regional dry period existed from approximately 5,000 to 2,000 years ago in which lake levels were up to 10 metres lower than present. Paleoclimatic reconstructions, while generalized, suggest annual temperatures during this warm period to be less than 2ºC above today’s temperatures while precipitation values may have been at least 10% lower.

While there is evidence for significant climatic changes and subsequent landscape response, there remain several insufficiencies with the available data. Firstly, they are predominantly based off of a limited number of sites scattered throughout the region while detailed understanding of the broader climatic picture requires the accumulation of data from many sites in order to distinguish local from regional climate signals. Additionally, inferred climate histories do not always line up from site-to-site introducing uncertainty into the regional picture. Lastly, the temporal resolution is often coarse and does not provide much information on medium-amplitude, medium-frequency events that are important as well.

More concerning, is the lack of information on river response to climatic changes in southern Ontario. The United Kingdom (and Europe in general) and the United States have been doing research on millennial- and centennial-scale river response and flood history for the last several decades while we remain in the dark on the behaviour of our river systems. This seems problematic considering, for example, the flood history of the Thames over the last 130 years, which has yielded several damaging floods.

Given the dearth and quality of available information on our water systems, and the apparent sensitivity of some of these systems to past climate change, it would behove governments at all levels to invest more money in research on paleoclimate-landscape interactions in order to gain a deeper understanding of how sensitive our region is to climate change across a range of temporal scales. This information can then be used to develop effective strategies in order to mitigate anticipated landscape responses.

If the past is the key to the future, then the sooner we understand the past, the sooner we can predict what future changes may bring, and the sooner we can prepare for them.

James Thayer
James Thayer

James Thayer is a Senior Research Fellow for the London Institute. He is a graduate of the universities of Western Ontario and Toronto where he received, respectively, his Honours Bachelor of Science in Geography and Geology and his Master of Science in Geography, specializing in fluvial and Quaternary geomorphology. He can be reached at james@londoninstitute.ca.

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