Bortolin Lakes and modern global climate change

Lakes and modern globalclimate change: 

Lakes and modern global climate change K. Bortolin

Recent History: 

Recent History One of the most controversial and heated debates in science Natural cycles vs. abnormal warming trend Earth as a self-regulating entity-will correct problem itself Increased warming rate will lend to destruction of natural communities

Are humans causing the problem?Vitousek, 1994 Ecology 75(7):1861-1876: 

Are humans causing the problem? Vitousek, 1994 Ecology 75(7):1861-1876

Are humans causing the problem?Vitousek, 1994 Ecology 75(7):1861-1876: 

Are humans causing the problem? Vitousek, 1994 Ecology 75(7):1861-1876 What anthropogenic activities are changing the environment? How are they changing it?

What are the sources and sinks of carbon?Cox et al. 2000 Nature 408:184-187: 

What are the sources and sinks of carbon? Cox et al. 2000 Nature 408:184-187 Ocean and land currently absorb 50% of carbon emissions By 2010, the land slows its uptake 2050-land becomes net source 2100-land matches ability of ocean to act as carbon sink

Why study the effects of climate change?: 

Why study the effects of climate change? To understand how the systems of the world react to temperature change If there is a significant change, management programs currently in place will have to change to accommodate new community structures

General Consensus: 

General Consensus Agree that the climate is generally warming and will continue to warm Must study effects of warming on ecosystems Can discover better management policies to fit changes, whatever they may be

Why look at lakes?: 

Why look at lakes? Lakes can be indicators for changes on a larger scale Currently the ocean is buffering the majority of our impacts Changes in lakes can be a sign of what to expect in the ocean in the future

Why should we care about climate change?: 

Why should we care about climate change? Species extinctions Weather pattern changes Natural disasters Food shortages Resource losses

Will all areas be affected equally?Quayle et al. 2002 Science 295:645: 

Will all areas be affected equally? Quayle et al. 2002 Science 295:645 Effects of global warming differ based on ecosystem type Arctic systems are most vulnerable as a small change alters the entire ecosystem Snow and ice cover alter environment Act as early warning devices of large scale changes Some of the most rapid changes worldwide

What about other ecosystems?: 

What about other ecosystems? Other than the Arctic, does average annual temperature effect the response of ecosystems to warming?

Lake Tanganyika, AfricaO’Reilly et al. 2003 Nature 24:766-768: 

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768 Physical Properties: Large (averaging 50x650km) Deep (mean 570m, max 1470m) Thermally stratified Oligotrophic Anoxic hypolimnion

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768: 

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768 Consequences of decreased productivity: Historical source of 25-40% of animal protein to surrounding countries. Possible decrease of 20% in primary productivity Decrease of 30% in fish yield

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768: 

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768 Is climatic warming to blame? Suggest that effects of climate change larger than those of anthropogenic activity and/or over fishing

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768: 

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768 What do the increase in temperature and decreased wind velocities mean? Increased stability of lake Stability increased 97% in non-windy season Reduced mixing depth Depth of oxygenated zone becoming shallower since 1939 (1.6 ± 0.2m per year)

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768: 

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768 Trends: Increased air temperature (0.5-0.7°C) Global average 0.6±0.2°C Decreased wind velocities (30%)

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768: 

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768 What would the expected results be? A decline in primary productivity If mixing is reduced, uplifting of nutrients to surface waters from deeper areas decreases

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768: 

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768 From carbon cores, there is an inferred loss of primary productivity in the past 80 years (low C:N) Correlation between isotope depletion and decreasing productivity and vice versa Fossil fuel burning decreases 13C ratio

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768: 

Lake Tanganyika, Africa O’Reilly et al. 2003 Nature 24:766-768 Previously studied relationships suggest 20% decrease in primary productivity lends to a 30% decrease in fishery yield If warming trend continues, a fishery that multiple countries rely on could collapse

Effects of Climatic Warming on Lakes of the Central Boreal ForestSchindler et al. 1990 Science 250:967-970: 

Effects of Climatic Warming on Lakes of the Central Boreal Forest Schindler et al. 1990 Science 250:967-970 Acknowledge changing climate Some models predict greatest increase in area of Ontario’s boreal forest Most extreme case predicts: Increase of 9°C Decrease soil moisture by 50%

Properties of Boreal Forests Schindler et al. 1990 Science 250:967-970: 

Properties of Boreal Forests Schindler et al. 1990 Science 250:967-970 Warm and arid Thin, sandy soils Low water capacity Higher frequency of forest fires when lower than normal precipitation

How are effects determined Schindler et al. 1990 Science 250:967-970: 

How are effects determined Schindler et al. 1990 Science 250:967-970 Data collection dates beginning between 1969 and 1971 Consistent measuring techniques Continuous records of: Weather Hydrology Chemistry Inflow/outflow Biology

What trends were present? Schindler et al. 1990 Science 250:967-970: 

What trends were present? Schindler et al. 1990 Science 250:967-970 Near consistent trends of warming and increased drought Increased forest fires Trends over the 20 study years were consistent with maximum warming prediction

Lakes of the Central Boreal Forest Schindler et al. 1990 Science 250:967-970: 

Lakes of the Central Boreal Forest Schindler et al. 1990 Science 250:967-970 What has changed? Temperature increased 2°C in 20 years Ice free season increased by 3 weeks More evaporation Less precipitation Increased forest fires

Lakes of the Central Boreal Forest Schindler et al. 1990 Science 250:967-970: 

Lakes of the Central Boreal Forest Schindler et al. 1990 Science 250:967-970 Effects of change Decreased water renewal rates Populations and diversity of phytoplankton increased Wind velocity increased Increased transparency

Lakes of the Central Boreal Forest Schindler et al. 1990 Science 250:967-970: 

Lakes of the Central Boreal Forest Schindler et al. 1990 Science 250:967-970 Increased chemical concentrations Deeper thermoclines Less habitat for stenothermic organisms

Lakes of the Central Boreal Forest Schindler et al. 1990 Science 250:967-970: 

Lakes of the Central Boreal Forest Schindler et al. 1990 Science 250:967-970 Increased evaporation and decreased water renewal rates: Expected to cause increased concentration of chemicals N:P ratio near doubled (25:1 to 50:1) N increased throughout the study period P increased slightly then drastically dropped, though not a statistically significant result

Lakes of the Central Boreal Forest Schindler et al. 1990 Science 250:967-970: 

Lakes of the Central Boreal Forest Schindler et al. 1990 Science 250:967-970 Same problem as in Lake Tanganyika, Africa: Increased water temperature decreases habitat for species that require colder temperatures Possible northward movement of species that can disperse

Lakes of the Central Boreal Forest Schindler et al. 1990 Science 250:967-970: 

Lakes of the Central Boreal Forest Schindler et al. 1990 Science 250:967-970 There are valuable fisheries in these lakes as well Unlikely that species of equal or greater economic value will replace displace species

Trends: 

Trends In both Lake Tanganyika, Africa and the ELA of the boreal forest, there was a decrease in economically important fish There were different events that led to the decrease Increase and decrease in primary productivity

Questions for the future:: 

Questions for the future: Is the rate of climate change too fast for species to adapt? Can we adopt a lifestyle that will minimize our effects on the environment before it’s too late?

The Big Picture: 

The Big Picture Cannot employ the wait and see plan Current evidence suggests that gross productivity of all ecosystem types will decline if warming trend continues Massive change will occur soon if models are correct (2100)