Part III: Climate

Introduction to Global Change and Invasions: Climate Change

In this section of the course, the focus is on the impact of climate change as a human-driven stressor affecting native communities. Prior lectures addressed biological invasions and their consequences, including habitat destruction, pollution, eutrophication, and overfishing. These factors contribute to the degradation of native communities and can lead to species extinctions. The upcoming lectures will explore how climate change interacts with biological invasions, particularly in aquatic systems.

Overview of Climate Change

Greenhouse Gas Emissions

Climate change is primarily driven by human activities leading to increased emissions of greenhouse gases, particularly carbon dioxide (CO2), over the past two centuries. These emissions are linked to significant climate alterations that can directly affect natural environments. Various consequences of climate change include:

  • Ocean Acidification: Increased CO2 levels lower the pH of ocean waters, affecting marine life.

  • Temperature Regime Changes: Rising temperatures lead to increased frequency and severity of extreme heat events.

  • Sea-Level Rise: Melting ice caps and glaciers contribute to rising sea levels, threatening coastal habitats.

  • Altered Precipitation Patterns: Changes in rainfall distribution and intensity affect water availability and ecosystem health.

  • Changes in Ocean Currents: Variations in circulation patterns can influence ecological interactions in marine environments.

  • Increased Storm Intensity: Stronger storms can disrupt habitats and increase pollution runoff.

Impact of Climate Change on Invasive Species

Transport and Introduction Mechanisms

Climate change affects the transport and introduction mechanisms for invasive species. Specific cases include:

  • Arctic Shipping Routes: The reduction of summer ice coverage is shortening the Northwest Passage, leading to increased shipping activity and higher risks of species invasions in northern Canada.

  • Great Lakes Water Levels: Forecasts predict decreased water levels due to higher temperatures and altered precipitation, leading to reduced cargo capacity for ships. This change could result in increased shipping frequency and a longer shipping season due to less ice coverage.

  • Sports Fishing Pressure: In northern temperate lakes, shorter periods of ice cover and reduced hypoxia due to warming may increase recreational fishing opportunities, subsequently affecting native species.

  • Ocean Circulation Patterns: Changes in these patterns may increase the dispersal and establishment success of non-native species in new regions.

Establishment and Spread of Invasive Species

Climate change also influences the establishment and success of invasive species. Factors involved include:

  • Warming Temperatures: As conditions become more favorable due to climate change, invasive species can establish more successfully. For example, research by Stachowicz demonstrated that warmer temperatures favored non-native tunicates, resulting in earlier recruitment and increased growth compared to native species.

  • Temperature Correlation: Native species often showed reduced recruitment rates at higher temperatures, whereas invasive species showed a positive correlation with warmer water conditions.

  • Feeding Experiments: Feeding studies indicated that invasive tunicates exhibited faster growth rates than native counterparts at elevated temperatures, particularly those approaching maximum summer values.

Temperature Tolerance in Invasive Species

Research by Sorte et al. highlighted that invasive species generally tolerate higher temperatures than native species. They found:

  • Latin for assignment temperatures at which species died ranged from 14ºC to 32ºC, demonstrating that invasive tunicates performed better than native species under increased temperature scenarios (+3ºC and +4.5ºC).

Impacts on Native Species

The adverse effects of climate change on native species become evident when assessing the competitive dynamics with non-native species. A recent review indicates that:

  • In aquatic environments, increases in temperature and CO2 concentrations negatively impact native species but have less effect on invasive species.

  • Consequently, aquatic ecosystems are predicted to be particularly vulnerable to invasions due to climate change.

Interaction of Climate Change and Invasive Species

Ocean Acidification Impacts

Ocean acidification not only affects individual species but can also increase predation risks. For instance:

  • In an experiment by Sanford et al., the predation of native Olympia oysters by the invasive Urosalpinx cinerea (Atlantic oyster drill) was measured. Oysters grown under higher CO2 levels were smaller and faced a 20% increase in predation susceptibility.

  • In contrast, invasive snails showed resilience to elevated CO2 levels with unchanged feeding behaviors, indicating that invasive species may find advantages in changing environmental conditions.

Projected Species Distributions

Future Species Range Shifts

Bellard et al. developed predictive models on the future distribution of species from the "100 world's worst invaders" list based on climate and land use data. Key findings included:

  • Climate change and land use changes are expected to cause drastic shifts in species distributions.

  • Predicted hotspots for future invasions include: Europe, northeastern North America, and Oceania, while some regions may see losses in invasive populations, particularly in tropical forests.

Trends in Invasive Species

Detailed assessments of the 100 worst invaders indicated significant trends:

  • Invasive amphibians and birds are projected to experience range contraction, while aquatic invertebrates and plants are expected to increase.

Warming and Tropical Introduced Species

Warming waters in tropical regions are facilitating the spread of species previously confined to Florida and the Bahamas. This phenomenon has been termed "Caribbean creeps" and is evidenced by:

  • Observations in various coastal areas where numerous species have been introduced due to increased temperatures post-1998, highlighting broader ecological shifts in response to climate change.

Conclusion

In summary, this lecture emphasized the multifaceted effects of climate change on species introductions, focusing on the alterations in temperature regimes, ocean acidification, and implications for invasive species dynamics. Effective management strategies must account for the potential interactions between climate change effects and invasive species to safeguard native biodiversity.