Of course! Here are comprehensive and engaging study notes on "Global issues" from the Applied Ecology topic, tailored for HKDSE Biology students of all ability levels and formatted in HTML as requested.

Global Issues: Our Planet, Our Responsibility

Hey everyone! Welcome to one of the most important topics in Biology: Global Issues. This isn't just about memorising facts; it's about understanding the big environmental challenges our world is facing right now. We'll look at problems like climate change and pollution, see what causes them, and explore how we can manage our planet more wisely. Why is this important? Because these issues affect our health, our environment, and our future. Let's dive in and see how biology helps us understand and solve these challenges!


1. Sustainable Development: The Big Idea

Before we look at the specific problems, we need to understand the main goal: sustainable development.

Imagine you get HK$100 in pocket money for the week. You could spend it all on Monday, but then you'd have nothing left for the rest of the week. A smarter way is to spend a little each day, so it lasts.

Sustainable development is the same idea, but for the whole planet! It means:

"Meeting the needs of the present without compromising the ability of future generations to meet their own needs."

In simple terms, it's about using the Earth's resources (like water, forests, and fish) in a smart way so that we have enough for ourselves, and so do our children and grandchildren in the future. It's all about finding a balance.

Key Takeaway

Sustainable Development is about balancing our current needs with the needs of the future, ensuring we don't use up all the resources. It's the ultimate goal for managing our planet.


2. Global Warming: The Earth's Fever

You've definitely heard about global warming. It simply means the average temperature of the Earth is increasing. Think of it like our planet having a slight, but persistent, fever.

What causes it? The Enhanced Greenhouse Effect

Don't worry, this isn't as complex as it sounds! Let's break it down.

The Normal Greenhouse Effect (This is a good thing!):

Imagine the Earth wearing a thin, invisible blanket. This "blanket" is made of gases in the atmosphere called greenhouse gases (like carbon dioxide). This blanket traps some of the sun's heat, keeping our planet warm enough for life to exist. Without it, the Earth would be a frozen ice ball!

The Enhanced Greenhouse Effect (This is the problem!):

Human activities are making this "blanket" way too thick. We are releasing huge amounts of extra greenhouse gases, which trap too much heat. This is what causes global warming.

Main culprits (human-caused greenhouse gases):

  • Carbon dioxide (CO₂): The biggest one! It comes from burning fossil fuels (coal, oil, and natural gas) in power plants, factories, and cars. Deforestation (cutting down forests) also makes it worse, because trees absorb CO₂. Fewer trees = more CO₂ in the atmosphere.
  • Methane (CH₄): Released from farming (like cows burping!) and rotting rubbish in landfills.
What are the problems (consequences)?
  • Melting Ice and Rising Sea Levels: Ice caps and glaciers are melting, causing sea levels to rise. This can lead to flooding in low-lying coastal cities, including parts of Hong Kong.
  • Extreme Weather: We see more frequent and more intense weather events, like stronger typhoons, severe heatwaves, and droughts.
  • Harm to Ecosystems: Coral reefs are "bleaching" and dying due to warmer water. Animals may be forced to move to find cooler habitats.
  • Impact on Farming: Changing weather patterns can make it harder to grow crops, affecting our food supply.

Did you know? Hong Kong's own coral communities, like those in Hoi Ha Wan Marine Park, have experienced coral bleaching during unusually warm summers, showing that this global problem has local impacts.

Key Takeaway

Humans burning fossil fuels and cutting down forests releases extra greenhouse gases. These gases trap too much heat, causing global warming, which leads to rising sea levels, extreme weather, and damage to ecosystems.


3. Acid Rain: When Rain Becomes Harmful

Normal rain is naturally slightly acidic, but acid rain is much more acidic and can be very harmful. It's caused by air pollution.

What causes it? A Chemical Recipe in the Sky

Here’s the step-by-step process:

Step 1: Factories, power plants, and vehicles burn fossil fuels.

Step 2: This releases pollutant gases, mainly sulphur dioxide (SO₂) and nitrogen oxides (NOx), into the atmosphere.

Step 3: These gases travel up into the clouds and react with water, oxygen, and other chemicals.

Step 4: They form sulphuric acid and nitric acid.

Step 5: This acidic water falls to the ground as acid rain (or snow, or fog).

What are the problems (consequences)?
  • Damages Forests: Acid rain can damage the leaves of trees and harm the soil, making it hard for forests to grow.
  • Harms Aquatic Life: It makes lakes, rivers, and streams too acidic, which can kill fish, insects, and other aquatic organisms.
  • Damages Buildings: It slowly corrodes and dissolves buildings and statues, especially those made of limestone or marble.
  • Affects Human Health: The pollutants that cause acid rain can contribute to respiratory problems like asthma.
Key Takeaway

Air pollutants (SO₂ and NOx) from burning fossil fuels mix with clouds to form acid, which falls as acid rain. This damages forests, kills aquatic life, and corrodes buildings.


4. Eutrophication: Too Much of a Good Thing

This sounds complicated, but the idea is simple. It’s what happens when a body of water gets overloaded with nutrients. Think of it as "over-fertilizing" a lake.

What causes it? A Step-by-Step Chain Reaction

Don't worry if this seems tricky at first, let's go through it one step at a time.

  1. Nutrient Overload: Untreated sewage and fertilizers from farms, which are rich in nutrients like nitrates and phosphates, get washed into a river or lake.
  2. Algal Bloom: These extra nutrients act like super-fertilizer for algae. The algae grow incredibly fast, forming a thick, green layer on the water's surface. This is called an algal bloom. A local example is a "red tide".
  3. Sunlight Blocked: The thick layer of algae blocks sunlight from reaching the plants living at the bottom of the lake.
  4. Plants Die: Without sunlight for photosynthesis, the underwater plants die.
  5. Decomposition: Huge numbers of bacteria start to break down (decompose) all the dead algae and dead plants.
  6. Oxygen Depletion: This decomposition process uses up a massive amount of dissolved oxygen in the water. The oxygen level drops so low that fish and other aquatic animals suffocate and die. This creates a "dead zone".

Memory Aid: Remember the steps with N-A-S-D-D!
Nutrients -> Algal Bloom -> Sunlight Blocked -> Death of plants -> Decomposition & Deoxygenation

What are the problems (consequences)?
  • Creates "dead zones" in water where most life cannot survive due to lack of oxygen.
  • Kills large numbers of fish and other aquatic animals.
  • Reduces biodiversity in the ecosystem.
  • Some algae in "red tides" produce toxins that can harm marine life and humans who eat contaminated seafood. (Tolo Harbour in Hong Kong has historically faced problems with red tides due to nutrient pollution).
Key Takeaway

Excess nutrients from sewage and fertilizers cause a massive growth of algae (algal bloom). When the algae die, their decomposition uses up all the oxygen in the water, killing fish and other animals.


5. Management of Resources: A Balancing Act

This brings us back to sustainable development. How do we manage our resources like fisheries and farms so they last for the future?

The Problem: Unsustainable Practices
  • In Fisheries: Overfishing is a huge problem. This means we are catching fish faster than they can reproduce. Destructive fishing methods, like trawling (dragging huge nets along the sea floor), destroy entire habitats.
  • In Agriculture: Using too many chemical fertilizers can lead to eutrophication. Overusing pesticides can kill beneficial insects and pollute the soil and water.
The Solution: Sustainable Management (with HK Examples!)

Here are some smart ways to manage our resources:

Managing Fisheries:

  • Ban destructive methods: For example, Hong Kong banned all trawling in its waters in 2012 to allow the seabed habitat to recover.
  • Create protected areas: Setting up marine parks where fishing is restricted or banned gives fish populations a safe place to breed. Local examples include Hoi Ha Wan Marine Park and Tung Ping Chau Marine Park.
  • Promote sustainable aquaculture: Farming fish in a responsible way can reduce the pressure on wild fish populations.

Managing Agriculture:

  • Organic Farming: This involves growing crops without using synthetic chemical fertilizers and pesticides. This protects the soil and prevents water pollution. You can find several organic farms in the New Territories.
  • Integrated Pest Management: Using natural predators (e.g., ladybugs to eat aphids) to control pests instead of just spraying chemicals.
Key Takeaway

To use our resources sustainably, we must stop harmful practices. For fisheries, this means creating marine parks and banning destructive methods. For agriculture, it means shifting towards organic farming to protect our environment.