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Biodiversity Under Threat: Concept Map

≈ 24 min
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Concept Map

Organise the vocabulary, quantities and relationships into a connected model.

This extension applies that lens specifically to Biodiversity Under Threat.

Biodiversity is lost when species disappear faster than new ones arise. The main causes in South Africa are:

  1. Habitat destruction — ploughing grassland, expanding towns, mining, and clearing wetlands. This is the single biggest cause worldwide.
  2. Invasive alien species — organisms brought from elsewhere that spread on their own and crowd out indigenous species. Water hyacinth chokes the Hartbeespoort Dam; black wattle and Port Jackson willow take over riverbanks and drink enormous volumes of water.
  3. Pollution — sewage and mine drainage in rivers, litter, and smoke.
  4. Over-harvesting — poaching of rhino and abalone (perlemoen), and over-fishing.
  5. A changing climate — species that cannot move or adapt fast enough lose their range.

Why it matters to people. Biodiversity does unpaid work for us every day: wetlands and healthy soils clean and store water; insects pollinate the crops in the Western Cape's orchards; indigenous plants supply medicines; and our wildlife supports a tourism industry that employs hundreds of thousands of South Africans.

Worked example — Working for Water. Alien wattle trees along a river each draw far more water than the indigenous plants they replaced. If one wattle takes 120 litres of water a day, then clearing 250 wattles returns

120×250=30 000 litres per day120 \times 250 = 30\,000 \text{ litres per day}

to the river. That is why crews are employed nationally to cut alien trees out of catchments: it is a water project as much as a conservation project.

Natural Sciences — Grade 7 — Concept Map: Which of these is an invasive alien plant in South Africa?

Natural Sciences — Grade 7 — Concept Map: What term describes a species brought in from another country that then spreads on its own and pushes indigenous species out?

Natural Sciences — Grade 7 — Concept Map: A stand of alien wattle trees grows beside a river. Each tree draws about 120 litres of water per day. A Working for Water team clears 250 of these trees. How many litres of water per day are returned to the river?

Name the original topic being extended by this concept map lesson.

Which statement is the best evidence-led starting point for Biodiversity Under Threat: Concept Map?