The idea
Biodiversity is the variety of life in a place — how many different species, and how much genetic variety within each one.
Why variety makes a system tough
Imagine two fields. One is planted with a single variety of wheat; the other holds forty species of grasses and wildflowers.
A new fungus arrives.
The monoculture has one answer to that question, and if the answer is “no resistance”, the whole field is lost. The meadow has forty answers, and some of them work. That is resilience, and it comes directly from variety.
The Irish potato famine
A single potato variety, grown almost everywhere, met a water mould it had no resistance to. Over a million people died. The biology of the failure was monoculture.
Measuring it
Species richness is the simplest measure: count the species. It ignores how common each one is, which is why ecologists also use indices that account for evenness.
| Plot | Species found | Individuals | Richness |
|---|---|---|---|
| Mowed lawn | 4 | 220 | Low |
| Unmowed edge | 17 | 190 | Higher |
| Woodlot floor | 23 | 145 | Highest |
Collect data like this yourself in Measuring Abiotic Factors.
Curriculum connection
B2.4
investigate factors and processes, including biodiversity, air and water quality, soil health, and succession, and explain how they contribute to ecosystem sustainability
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B1.1
assess impacts of climate change on the sustainability of local and global ecosystems, describe local or global initiatives for combatting climate change, and identify solutions to address some of the impacts
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