Effects of climate change on the environment, plants and animals

Welcome to the Changing World!

Hello there! Today, we are diving into one of the most important topics in your H2 Biology journey: how climate change actually affects the world around us. It’s easy to hear the words "global warming" and think only of polar bears, but as an A-Level student, you’ll see it's a complex chain reaction affecting everything from the microscopic metabolism of a mosquito to the vast underwater cities of coral reefs.

Don’t worry if this feels like a lot of "doom and gloom" at first. We will break it down into simple, logical steps so you can master the biological mechanisms behind these changes. Let’s get started!

1. Physical Changes in the Environment

Before we look at the animals and plants, we need to understand how the "house" they live in is changing. When greenhouse gases (like \(CO_2\) and methane) trap heat, the Earth’s physical systems react in several ways:

A. Melting Polar Ice Caps and Rising Sea Levels

As global temperatures rise, huge chunks of ice at the poles melt. This adds more water to the oceans. Additionally, water expands when it gets warmer (thermal expansion). Analogy: Think of a glass of water filled to the brim. If the water warms up or you add more ice cubes that melt, the water eventually spills over.

B. Extreme Weather Events

Climate change isn't just "getting warmer." It’s about energy. More heat in the atmosphere means more energy for storms, leading to more frequent and intense hurricanes, droughts, and heavy rainfall.

C. Stress on Fresh Water Supplies

Many people and animals rely on glaciers for fresh water. As these glaciers disappear, and as rising sea levels push saltwater into freshwater rivers (saltwater intrusion), fresh water becomes a rare and "stressed" resource.

D. The "Permafrost Problem"

In very cold regions, the ground is permanently frozen (permafrost). This ground contains huge amounts of frozen organic matter (dead plants and animals). As it thaws, microbes decompose this matter, releasing even more \(CO_2\) and methane. Key Term: This is a positive feedback loop—warming causes the release of gases, which causes even more warming!

Quick Review:
• Melting Ice: Leads to sea level rise.
• Extreme Weather: More energy in the system = wilder weather.
• Permafrost: Thawing releases "locked up" greenhouse gases.

2. Impacts on Sensitive Ecosystems

Some ecosystems are like the "canaries in the coal mine"—they are the first to suffer when the temperature shifts even slightly.

A. Coral Reefs (The Bleaching Crisis)

Corals have a beautiful partnership (symbiosis) with tiny algae called zooxanthellae. The algae provide food, and the corals provide a home. When the water gets too warm, the corals get stressed and kick the algae out. This makes the coral turn white—this is coral bleaching. Without the algae, the coral often dies.

B. Mangroves and Seagrasses

These coastal "nurseries" are being hit by rising sea levels. While mangroves are tough, if the sea rises too fast, they can't "move" inland quickly enough and end up drowning. Did you know? Mangroves are actually superheroes! They trap carbon in their roots, helping to mitigate climate change. But they can only take so much stress.

Key Takeaway: Climate change causes environmental stress, which disrupts the delicate symbiotic relationships and physical boundaries of marine ecosystems.

3. How Plants and Animals Respond

When the environment changes, living things have three choices: Move, Adapt, or Die.

A. Migration Patterns

Many species are moving toward the poles or higher up mountains to find the cool temperatures they prefer.
• Fishes: Moving to deeper or more northern waters.
• Insects: Shifting their ranges. This can be dangerous if they move into areas where they have no natural predators or where they spread diseases.

B. Food Chains and Niche Occupation

Every organism has a niche (a specific role and "address" in the environment). Climate change can cause ecological mismatch. Example: A bird might migrate to a forest to eat caterpillars, but because of the warmer spring, the caterpillars hatched and turned into butterflies two weeks early. The bird now has nothing to eat!
This breaks food chains and can lead to the loss of biodiversity.

Common Mistake to Avoid: Don't just say "animals die." Be specific! Explain that environmental stress (temperature/weather) leads to a change in niche occupation or a disruption in food chains.

4. A Closer Look: Insects and Disease Vectors

This is a favorite topic for examiners! Why does temperature matter so much to an insect like a mosquito?

A. Metabolism and Temperature

Insects are ectotherms (their body temperature depends on the environment).
1. Higher Temperature = Faster Metabolism: Chemical reactions inside the insect speed up.
2. Faster Life Cycle: Because their metabolism is faster, they grow, move, and reproduce much more quickly.
3. Narrow Tolerance: Most insects have a very specific temperature "sweet spot." If it gets too hot, they die, but a slight increase often helps them thrive and spread.

B. Case Study: Aedes aegypti (The Dengue Mosquito)

The Aedes aegypti mosquito carries viruses like Dengue and Zika. Global warming affects it in three ways:
• Faster Development: Larvae mature into adults faster in warmer water.
• Increased Biting Frequency: Higher temps make the mosquito hungrier and more active.
• Expanded Range: Places that used to be too cold for mosquitoes (like higher altitudes or temperate countries) are now warm enough for them to survive.

Memory Aid: The 3 'F's for Mosquitoes
Faster growth, Further range, Frequent biting!

5. Impact on Food and Medicine

Finally, why should humans care? Because our survival depends on biodiversity.

A. The Tropical Reservoir

The tropics are incredibly rich in biodiversity. Many of our modern biomedicines (medicines derived from plants or animals) come from tropical species. If climate change causes these species to go extinct, we lose the "blueprints" for future cures before we even discover them!

B. Global Food Supply

Environmental stress makes it harder to grow crops.
• Heat stress: Reduces crop yields (e.g., rice and wheat).
• Genetic Diversity: We need a wide variety of wild plants to cross-breed with our crops to make them "climate-proof." If those wild plants disappear, our food supply becomes vulnerable.

Summary Checklist

Can you explain:
1. Why melting permafrost creates a "feedback loop"? (Hint: Methane release)
2. Why corals turn white when stressed? (Hint: Symbiosis with algae)
3. How temperature affects the life cycle of the Aedes aegypti? (Hint: Metabolic rate)
4. What happens to a food chain during an "ecological mismatch"?

You’re doing great! This chapter is all about connections. If you can link a physical change (like temperature) to a biological process (like metabolism), you are well on your way to an A!