How did Africa's grasslands get started? | 5/16/2019 | Staff
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Between 10 million and 6 million years ago, vegetation across much of the world underwent a transformation, as warmth-adapted grasses displaced previously dominant plants, shrubs and trees. The new grasses carried out the chemical reactions required for photosynthesis in a distinct new way. Scientists have labeled this new process the C4 pathway. In East Africa, the changeover coincided with the evolution of mammal lineages that we recognize today, including early human ancestors. Today, C4 plants comprise about one-quarter of the Earth's vegetation, from the Great Plains of North America to western China, Australia and much of sub-Saharan Africa.

What is the origin of these plants, and why did they spread so far and wide? A new study in the journal Nature Geoscience tries to get at this question by looking at deep-sea sediments off east and west Africa, which contain traces of past plant life and the conditions under which it existed. It shows that both northwestern and eastern Africa experienced a spread in C4 plants starting around 10 million years ago, at a time when carbon dioxide in the atmosphere was dipping, but there were no apparent changes in rainfall or dust deposition.

Co-author - Cassaundra - Rose - Research - PhD

We spoke with co-author Cassaundra Rose, who did the research as a Ph.D. student at Columbia University's Lamont-Doherty Earth Observatory. The study was carried out also by Lamont-Doherty scientists Pratigya Polissar (who is the lead author), Kevin Uno, Samuel Phelps and Peter deMenocal.

What are C4 plants, and what makes them important?

Plants - Water - Carbon - Dioxide - Photosynthesis

Plants need sunlight, water and carbon dioxide to perform photosynthesis, but there are differences in the very first step of photosynthesis, when the plant converts CO2 into useable molecules. About 85 percent of all plants use what we call C3 photosynthesis. C4 plants use a slightly different kind that produces a 4-carbon compound in that first step. Hence...
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