The Neogene Period 23.03 million years ago – 2.58 million years ago

The Neogene Period 23.03 million years ago – 2.58 million years ago. The Neogene officially covers about 20 million years. During this period, mammals and birds continued to evolve into roughly modern forms . Early hominids, the ancestors of humans, appeared in Africa. Some continental movement took place, the most significant event being the connection of North and South America at the Isthmus of Panama. This cut off the warm ocean currents from the Pacific to the Atlantic Ocean, leaving only the Gulf Stream to transfer heat to the Arctic Ocean. The global climate cooled considerably. The earth was locked in an Ice Age. Glaciers, growing from the ice caps, reached down as far as Ohio in the United States. There was new plant growth in the ocean. Kelp forests grew in cool waters where the plant could attach to rocks and coral. Otters and other animals evolved to live in this unique ecosystem. The dugong, a marine mammal related to the elephant and modern manatees, lived in large numbers. Modern versions of these animals still feed on the plants in the Great Barrier Reef off the Australian coast. Sharks developed new species. One of these new sharks was Charcharodon Megalodon, the largest of all the sharks. It grew to be nearly 50 feet long dining on whales and dugongs. F o r t u n a t ely i t d i d n o t s u r v i v e i n t o t h e m o d e r n e r a . Although whales started to evolve in the preceding Paleogene period, they didn’t become exclusively aquatic creatures until the Neogene, which also witnessed the continuing evolution of the first pinnipeds (the mammalian family that includes seals and walruses) as well as prehistoric dolphins. 14 Kelp Beds – End of the line after 20 million years? U.S. studies suggest today’s kelp beds are less extensive than those in the recent past Source; UC Davis News, http://ccbio340.weebly.com/giant-kelp.html Kelp forests occur worldwide throughout temperate and polar coastal oceans. Giant kelp growth is so dense that they are known for their kelp forests, which are home to many marine animals that depend on the algae for food and shelter. Giant kelp is one of the fastest growing organisms on Earth able to manage up to a metre a day in growth and in depths up to 30 metres in Tasmania. Unlike most plant root systems that carry nutrients back and forth through the plant, the holdfast that anchors it to the rock doesn’t carry nutrients or water. It thrives in cooler waters where the ocean water temperature remains below 21 °C. Giant kelp can live up to 7 years. The kelp forests are considered to be some of the most diverse and productive ecosystems on the planet. They love a cool climate and tripled in size from the peak of glaciation 20,000 years ago to about 7,500 years ago. Then as the world has warmed they have shrunk by up to 70 percent to present day levels. Kelp forests around Californian offshore islands peaked around 13,500 years ago as rising sea levels created new habitat. Since then they have declined. The kelp along the mainland coast peaked around 5,000 years later. On land, scientists can reconstruct the history of a forest or grassland from fossilized pollen or leaves. But kelp do not make pollen, and marine sediments do not preserve a good record of the plants. The researchers used depth charts of the southern California coastline and information from sediment cores on past nutrient availability to reconstruct potential kelp habitat as sea levels changed over the last 20,000 years. There was transition from an extensive island-based kelp forests to a mainland-dominated system. When compared to the archaeological record it gave a more complete picture of California’s coast. People lived off the produce of kelp forests when resources on land dwindled, and those changes are recorded in shell middens. Climate-driven shifts in kelp ecosystems impacted on human populations that used those resources. Kelp is still diminishing around the world as our globe warms. The eastern Australian coast is a hot spot for these changes due to warm tropical currents bathing these regions