Human history is intricately linked to biogeography. Climate and the history of land masses on Earth have had large roles in shaping human history and evolution. For example, there was once a land bridge over the Bering Sea that connected Asia to North America. Scientists believe that about 10,000 years ago people crossed that land bridge as they hunted herds of large mammals like mammoths, mastodons and bison.
Here is where the story gets a little controversial: while most scientists agree that these people were the first humans in North America, and their descendents spread southward into Mexico and South America, there are some other theories out there. Spearheads that were found in Clovis, New Mexico were dated to 13,500 years ago, meaning humans must have been in North America much earlier than previously thought. Other archeological finds in Monte Verde, Chile and in Washington state are evidence for an earlier crossing of the land bridge, or reaching North America by sea instead of land. Read more about these theories here.
The Bering Land Bridge National Preserve in Alaska protects area that was part of the ancient land bridge between Asia and North America. Image from here.
Trade is one of the dominant forces that shaped our world into what it is today. Explorers ventured into unknown territories, countries were seized and colonized, and political alliances were formed because people wanted things. What things? Well, everything, but especially spices. The spice trade between ancient civilizations in Europe, northern Africa, and Asia went on for centuries before the Americas were "discovered" by Europeans. Cinnamon from Sri Lanka, turmeric from Pakistan and India, cardamom from India and ginger from China were highly sought-after spices that made Europeans go gaga. Ginger was so highly prized in medieval times that one pound of ginger cost the same as a live sheep.
Turmeric from Pakistan.
Vanilla and chocolate are both native to the Americas, and became important trade items in the 1500s. Both are now cultured in Africa and Asia, with different varieties such as Tahitian and Madagascar vanilla. We're not sure, but we're guessing baked goods were not so tasty before the discovery of chocolate and vanilla.
Chocolate (Theobroma cacao) pods. The beans are inside the white fleshy parts.
Most of the world's cuisines are defined by particular ingredients that are unique to that region—curry spices in Indian food, cilantro in Mexican food, and maple syrup in Canadian food (okay, that one might be a stretch). The reason that certain spices and ingredients are so prevalent in these regional foods is because they grow well there.
Of course, in our modern globalized society, ingredients travel all over the world. Not everything in a culture's cuisine is native to that area. Tomatoes, for example, did not appear in Italian food until after colonialism…tomatoes are native to South America and were spread around the world thanks to Spanish trade. Imagine spaghetti and meatballs without tomato sauce.
Modern agriculture has definitely revamped the accessibility of many foods. However, there are still some ingredients that are only cultivated in certain places, including two of the world's most important vices: chocolate and coffee.
Chocolate has a long history, going back to the Aztecs, but was spread to Europe and the rest of the world thanks to Christopher Columbus. And boy, did it spread. Americans eat 12 pounds of chocolate a year. Yum. Even though chocolate is well-loved by Americans (and Europeans…we're looking at you, Belgium), it doesn't grow in Europe or the US. Chocolate comes from the fruit of the cacao tree, Theobroma cacao. The cacao tree is a tropical rainforest tree and grows best in shade (like the shady understory of a forest). Even though people cultivate cacao on plantations, cacao is only grown in tropical climates and is still harvested by hand. That's right, no heavy machinery here.
A cacao pod hanging from the tree.
Similar to chocolate, coffee trees also grow in the tropics. The coffee tree, Coffea arabica, is native to Ethiopia but other 102 other species in the Coffea genus exist all over Africa. Though coffee is native to Africa, most coffee is now produced in tropical countries of Central and South America. Coffee trees are not just tropical, but need humid forests in the mountains between 950-1950 meters above sea level. Given this specific habitat that coffee trees need, it's amazing that so many people all over the world consume coffee.
Other vital crops also grow in specific climates; they are just more widespread. Grains such as wheat and corn need the right temperature and precipitation regime to grow and produce the food we need. Some climate change scenarios predict that the climate of the Great Plains, the current breadbasket of North America, will shift northward into Canada in the future. We might be eating a lot more Canadian corn syrup and a lot less maple syrup if that happens.
Iowa, Illinois and Minnesota are the largest producers of corn (for human consumption) for now. This map may look a lot different in 100 years.
As you know from reading about biogeography, the Earth's continents and climate have not always been the same. Climate has changed many times throughout Earth's history, and some species have gone extinct while others have evolved. Current climate change is a bit different from other climate changes in the past.
For one thing, human activity is responsible this time around—fossil fuel burning released tons of carbon dioxide into the atmosphere, heating up the planet. However, this is not the first time an organism's activity changed the atmosphere. Over thousands of years, the growth and reproduction of lots of cyanobacteria early on in the history of life on Earth released a lot of oxygen into the atmosphere, and paved the way for oxygen-breathing life to move onto land.
Another difference with current climate change is the speed at which it is happening. According to the US Environmental Protection Agency (EPA), temperatures in the US have been rising since the early 1900s, but most rapidly since the 1970s. Even if we stop putting greenhouse gases into the atmosphere today, temperatures will continue to rise for at least 50 years.
Image from here.
So what does this mean for the distribution of species around the Earth? Species basically have three options: adapt, move, or go extinct. We will probably see some of each of these things happen. Bird species in the US have started spending their winters further north than they used to because of warmer temperatures. A few species have moved as far north as 400 miles, but others have not moved at all. Plants are also able to survive further north, as average low temperatures have increased.
Conservation biologists who try to preserve habitat for endangered species are left with a dilemma: do they focus on where species live now or where they might live in the future? How far into the future can they hope to have an influence? These are questions that land managers, scientists, and policy makers have to consider. Unfortunately, there is no easy way to deal with climate change or predict how it will influence every species.