D4.3.11 Increases to the number of insect life cycles within a year due to climate change (HL) Notes

Increases to the Number of Insect Life Cycles Within a Year Due to Climate Change

1. Consider for a moment that a forest under siege by tiny invaders which are the spruce bark beetles.
2. These insects, once limited by colder climates, are now thriving, completing more life cycles each year due to rising temperatures.
3. This isn't just a story about beetles; it's a glimpse into how climate change is reshaping ecosystems.

How Climate Change Accelerates Insect Life Cycles

Warmer Temperatures and Faster Development

1. Insects are ectothermic, meaning their body temperature and metabolic rates depend on the environment.
2. Warmer temperatures speed up their development, allowing them to complete life cycles more quickly.

Synchronization of Generations

Warmer temperatures also synchronize insect populations, leading to simultaneous emergence and larger outbreaks.

Longer Breeding Seasons

Climate change extends the breeding season for many insects, allowing for additional generations within a year.

Example 1: Mosquito Species and Disease Vectors

1. Mosquitoes (Aedes aegypti) are vectors for diseases like Dengue and Zika. As climate change causes temperatures to rise in regions such as South America (Brazil, Argentina), these mosquitoes can complete more life cycles in a year.
2. Warmer temperatures allow eggs to hatch more quickly and larvae to develop faster, leading to more frequent mosquito generations.
3. This increased mosquito population density can lead to a higher risk of disease transmission.
4. For example, more mosquitoes mean more bites and a greater chance of spreading Dengue virus.

Impact on Public Health

1. Higher mosquito numbers can directly result in a greater incidence of Dengue, Zika, and other mosquito-borne diseases in affected regions.
2. Increased transmission rates lead to health crises and a need for stronger public health interventions and vector control measures.

Example 2: The Spruce Bark Beetle

Life Cycle of the Spruce Bark Beetle

1. The spruce bark beetle (Dendroctonus micans) is a pest species that feeds on spruce trees.
2. It is a forest-destroying insect that has a profound impact on the health of forest ecosystems.
3. Temperature increases due to climate change are affecting the life cycle of these beetles.
4. Warmer winters mean fewer frosts, which leads to higher survival rates of overwintering beetles and allows them to breed more quickly.
5. As a result, the beetles can complete multiple life cycles per year, increasing their population density and causing greater damage to forests.
6. Spruce trees weakened by repeated attacks are more susceptible to disease and degradation, leading to forest collapse in some areas

Impact on Forests

The combination of synchronized emergence and increased generations leads to severe tree mortality. This creates cascading effects on the ecosystem:

1. Loss of Habitat: Dead trees reduce shelter for birds and mammals.
2. Increased Fire Risk: Deadwood becomes fuel for wildfires.
3. Carbon Release: Decomposing trees release stored carbon, exacerbating climate change.

Why Does This Matter?

Feedback Loops in Climate Change

The destruction of forests by beetles creates a positive feedback loop:

1. Dead Trees: Release carbon dioxide as they decompose.
2. Reduced Carbon Sequestration: Fewer trees mean less carbon is absorbed from the atmosphere.
3. Warming Climate: Increased carbon dioxide accelerates global warming, further boosting beetle populations.

Broader Ecological Impacts

The effects of increased insect life cycles extend beyond forests:

1. Biodiversity Loss: Species dependent on spruce trees decline.
2. Altered Water Cycles: Tree loss affects transpiration, reducing rainfall and increasing drought risk.
3. Economic Costs: Forestry industries suffer from reduced timber yields and increased management expenses.