In 1802, a team of scientists and explorers set out to climb a mountain in South America that at the time was thought to be the highest in the world. Mt. Chimborazo is located near the equator in what is today the country of Ecuador. The team was led by German naturalist and explorer, Alexander von Humboldt, who had been traveling through South America, making detailed observations of its geography, flora, and fauna. Humboldt and his companions Carlos de Montúfar and French botanist Aimé Bonpland began their climb on June 23rd, 1802. They carried with them an assortment of scientific instruments, including devices to measure the temperature, air pressure, humidity, and the chemical composition of the air. Humboldt knew that if they reach the top, they would be the first people to do so. Humboldt not only wanted to set foot on the summit of what he thought was the world's highest mountain, he also wanted to learn as much as he could about what the environment was like at such a high elevation. Humboldt and his companions had climbed other mountains in the region and had already made some interesting observations about how conditions change with increasing elevation. Everywhere he went, Humboldt made note of what type of plants were growing, recording the species and the elevation where it was found but none of these mountains were as tall as Chimborazo. While making his way up that's steep slopes, Humboldt had an epiphany. He noticed that the plants that grew at high elevation resembled plants he had seen in Europe. There was a moss that looked a lot like a species he had seen in northern Germany. Others included lichens, the only organisms found near the snow cap, and they resembled species from the Arctic. Humboldt recognized that the physical conditions like the temperature were similar on the high slopes of Chimborazo and in Northern Europe. In other words, as you move up in altitude, it's like moving up in latitude. Chimborazo is just south of the equator, so its lower slopes are covered in tropical forests. Moving upward, you cross through almost every type of ecosystem on Earth. From hot wet rain forests to cold, dry tundra. It's as if you had traveled from the equator to the North Pole by traveling up rather than traveling North. Alexander von Humboldt was the first to describe the similarities between altitude and latitude and most importantly, he was the first to suggest that the changes in the physical environment that go along with altitude and latitude are responsible for the corresponding changes in vegetation. In other words, it wasn't a coincidence that the high slopes of Chimborazo reminded Humboldt of the Arctic. He was saying that the same types of plants grow in both places because they share the same physical conditions like low temperature. Humboldt and his companions didn't quite make it to the top of Chimborazo. They were forced to turn around after reaching an enormous chasm that blocked their path. They were also suffering from injuries and severe altitude sickness. But despite not reaching the summit, the climb proved to be a pivotal moment in Humboldt's life and in the history of science. After they descended, Humboldt gathered his notes and begin drafting a sketch that incorporated everything he had observed. The changes in temperature, air pressure, and humidity with increasing elevation, the location of different species of plants, including the highest elevation where each had been observed and he added the same types of observations that he had made on other mountains, both in the Andes and in other parts of the world. Humboldt's greatest insight was to recognize the interconnectedness of the natural world. Plants and other living things depend on the climate and soil. Distant places are connected to one another by sharing similar environments, leading to similarities in their flora and fauna. By making these connections, Humboldt was laying the foundation for a new kind of science, the science of ecology.