Human Impact on the Environment - Study Notes

Hey everyone! Welcome to one of the most important topics in Biology - how we, as humans, affect the world around us. This isn't just about exams; it's about understanding our planet and our role in protecting it. We'll break down how our growing population, our use of resources, and our cities are changing the environment. We'll also look at the problems this creates and, most importantly, what we can do about it. Let's get started!

a. Human Impact on the Environment

1. The Population Explosion: More People, More Problems

Think of the Earth as one big house. When only a few people live in it, there's plenty of room, food, and resources for everyone. But as the number of people grows rapidly, the house starts to feel crowded. This is what's happening with the human population growth.

Impacts of Rapid Population Growth:
  • More resources needed: More people need more food, water, energy, and space to live. This puts a huge strain on Earth's natural resources.
  • More waste produced: More people means more rubbish, more sewage, and more pollution from factories and cars.
  • More habitats destroyed: To build homes, farms, and cities for everyone, we often have to clear forests and other natural areas, leaving animals with nowhere to live.

Because of these challenges, it's important to think about population control. This means managing the growth of the human population so that our planet's resources can sustain us in the long term. This is a complex issue, but it's a key part of creating a sustainable future.

Key Takeaway

A rapidly growing human population increases the demand for resources and produces more waste, leading to environmental problems like resource depletion and habitat loss.

2. Using Up Our World: Resources & Their Management

We use resources from the environment every day. These can be sorted into two types:

  • Renewable resources: These can be replaced naturally over a relatively short time. Examples: sunlight, wind, wood (if we replant trees).
  • Non-renewable resources: These exist in a fixed amount and cannot be easily replaced once they're used up. Examples: fossil fuels (coal, oil), minerals.
Focus on Fisheries and Agriculture

Two key ways we get our food are through fishing and farming, but they can cause problems if not managed well.

  • Fisheries - Overexploitation: This means we are catching fish faster than they can reproduce. Imagine a bank account where you keep taking out more money than the interest you earn - eventually, it will run out. That's what's happening to many fish populations.
  • Agriculture - Environmental Degradation: To grow more crops, farmers often use chemical fertilisers and pesticides. These chemicals can wash into rivers and soil, causing pollution. This is a form of environmental degradation, which means making the environment worse.
A Hidden Danger: Accumulation of Toxins

This is a super important concept. When toxic (poisonous) chemicals like pesticides get into the environment, they can build up in organisms. This gets worse as you go up the food chain.

The process is called bioaccumulation (building up in one organism) and biomagnification (becoming more concentrated up the food chain).

Don't worry, it's simpler than it sounds! Here’s how it works:

  1. A pesticide is sprayed on a farm and washes into a lake.
  2. Tiny plankton absorb a tiny bit of the pesticide.
  3. Small fish eat LOTS of plankton. The pesticide from all that plankton builds up in the fish's body.
  4. A big fish eats LOTS of small fish. The pesticide becomes even MORE concentrated in the big fish.
  5. A bird eats LOTS of big fish. The bird ends up with a very high, potentially deadly, concentration of the pesticide.

Analogy: Imagine each plankton has 1 drop of poison. A small fish eats 10 plankton, so it has 10 drops. A big fish eats 10 small fish, so it has 100 drops! The poison gets "magnified" up the food chain.

Key Takeaway

Unsustainable use of resources, like overfishing and chemical pollution from farming, damages ecosystems. Toxic substances can accumulate and become more concentrated at higher levels of the food chain (biomagnification).

3. Building Our Cities: Urbanisation and Industrialisation

As the population grows, more people move to cities (urbanisation) and we build more factories (industrialisation). This has big effects on the environment.

  • Land Clearance and Reclamation: To make space for buildings and roads, we cut down forests (land clearance). In coastal cities like Hong Kong, we also fill in parts of the sea to create new land (land reclamation). Both of these actions destroy natural habitats for plants and animals.
  • Pollution and Health Problems: Cities and factories are major sources of pollution.
    • Air Pollution: Burning fossil fuels in cars and factories releases harmful gases. This can cause respiratory illnesses like asthma and bronchitis.
    • Water Pollution: Untreated sewage and chemical waste from factories can get into rivers and the sea. Drinking or swimming in this polluted water can cause diseases like gastroenteritis (stomach flu).
Did you know?

Much of the land we stand on in areas like Central, Wan Chai, and Kai Tak in Hong Kong was created through land reclamation!

Key Takeaway

Urbanisation and industrialisation lead to habitat destruction through land clearance and reclamation. They also cause air and water pollution, which can lead to serious human health problems.

b. Pollution Control

4. The 4 Rs: A Simple Guide to Helping the Planet

To control pollution, we can follow four simple principles. You might have heard of 3, but 'Replace' is also important!

  • Reduce: Use less stuff! For example, turn off lights when you leave a room to reduce electricity use.
  • Reuse: Use items again instead of throwing them away. For example, use a reusable water bottle instead of buying single-use plastic ones.
  • Recycle: Process used materials to make new products. For example, putting paper, plastic, and metal in the correct recycling bins.
  • Replace: Use sustainable alternatives instead of harmful ones. For example, replace fossil fuel energy with solar or wind power.

5. What Happens After You Flush? Sewage Treatment

We can't just dump all our toilet and kitchen waste (sewage) into the sea. It's full of harmful bacteria and organic waste that would pollute the water and kill marine life. So, we treat it first!

The key biological principle of sewage treatment is using helpful microorganisms (like bacteria) to do the cleaning for us.

Step-by-step idea: 1. Sewage enters the treatment plant. 2. It's held in large tanks where air is bubbled through it. 3. This encourages helpful aerobic bacteria to grow and multiply. 4. These bacteria feed on the harmful organic matter in the sewage, breaking it down into safer substances like carbon dioxide and water.
Think of it as a giant, controlled ecosystem where we use an army of good bacteria to eat all the bad stuff!

Key Takeaway

We can control pollution using the 4 Rs (Reduce, Reuse, Recycle, Replace). Sewage treatment uses beneficial microorganisms to break down harmful waste, preventing water pollution.

c. Conservation

6. Why Bother Saving Species? The Importance of Biodiversity

Biodiversity is the variety of all living things on Earth – from the tiniest bacteria to the biggest whale. Preserving it is incredibly important for several reasons:

  • Economic Issues: A healthy environment provides resources for medicines, food, and materials. It also supports tourism (people pay to see beautiful nature and unique animals).
  • Ecological Issues: Every species has a role in its ecosystem. High biodiversity makes an ecosystem more stable. Analogy: Think of an ecosystem as a Jenga tower. If you only pull out one or two blocks (species), it might stay standing. But if you remove too many, the whole tower will collapse.
  • Aesthetic Issues: Nature is beautiful! We have a responsibility to preserve its beauty for future generations to enjoy.
  • Moral Issues: Many people believe that humans do not have the right to cause the extinction of other species.

7. Protecting Our Neighbours: Conservation of Species & Habitats

Conservation is the protection of natural resources, habitats, and species.

Conservation of Species

This focuses on protecting animals and plants that are in danger of disappearing forever (endangered species). In Hong Kong, this includes the Chinese White Dolphin and Romer's Tree Frog.
Measures to protect them include:

  • Creating laws to ban hunting and trade.
  • Establishing captive breeding programmes.
  • Protecting the specific areas where they live.
Conservation of Habitats

If you want to save the animals, you have to save their homes! This involves:

  • Creating conservation areas: These are places protected by law. Examples in Hong Kong include our beautiful Country Parks, Marine Parks, Sites of Special Scientific Interest (SSSI), and the Mai Po Marshes (a Ramsar site), which is vital for migratory birds.
  • Ecological restoration: This means actively trying to repair damaged ecosystems. For example, replanting a forest that was destroyed by a fire or pollution.

8. It's Everyone's Job: Roles in Conservation

Conservation is a team effort!

  • Individuals: We can all play a part by following the 4 Rs, educating ourselves and others, and supporting conservation organisations.
  • Government: The government plays a crucial role by passing environmental laws, establishing and managing protected areas (like country parks), and funding conservation research.
Key Takeaway

Conservation is vital for economic, ecological, aesthetic, and moral reasons. It involves protecting both individual species and their habitats, and requires effort from both individuals and the government.

d. Global Issues

9. The Big Picture: Major Global Environmental Problems

Some environmental problems are so big they affect the entire planet. Here are the key ones you need to know:

  • Global Warming:
    • Cause: The burning of fossil fuels releases "greenhouse gases" (like carbon dioxide). These gases build up in the atmosphere and act like a blanket, trapping heat and warming the Earth.
    • Problem: Leads to climate change, melting ice caps, rising sea levels, and more extreme weather events.
  • Acid Rain:
    • Cause: Pollutants from factories and power plants (like sulphur dioxide) mix with water droplets in the clouds, making the rain acidic.
    • Problem: Acid rain damages forests, harms life in lakes and rivers, and can even erode buildings.
  • Eutrophication and Algal Bloom:

    This is a chain reaction that destroys aquatic ecosystems. It's often caused by fertiliser run-off from farms.

    1. Fertilisers (rich in nitrates and phosphates) wash into a lake or the sea.
    2. Algae love these nutrients and start growing uncontrollably. This is called an algal bloom.
    3. This thick layer of algae on the surface blocks sunlight from reaching the plants below, which then die.
    4. Bacteria decompose all the dead algae and plants. This decomposition process uses up a huge amount of dissolved oxygen in the water.
    5. Fish and other aquatic animals suffocate and die due to the lack of oxygen.
Quick Review: Eutrophication

Fertiliser → Algal Bloom → Sunlight Blocked → Plants Die → Bacteria Decompose & Use O₂ → Fish Die. The algae don't poison the fish; the lack of oxygen from decomposition kills them!

10. Working Towards a Better Future: Sustainable Development

So how do we solve all these problems? The key idea is sustainable development.

Definition: Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

In simple terms, it means living our lives and running our societies in a way that we can continue to do forever without running out of resources or destroying the planet. This includes the careful management of resources like fisheries and agriculture, to ensure they remain productive for years to come. For example, setting fishing quotas to prevent overexploitation.

Key Takeaway

Global issues like global warming, acid rain, and eutrophication affect the entire planet. The goal is to achieve sustainable development, where we use resources wisely to ensure a healthy planet for ourselves and for future generations.