By Erika Lyon
It is a concern that we are entering Earth’s 6th mass extinction. Mass extinctions occur when a large number of species die off in a short amount of time relative to background extinction rates (to read more about extinctions, click here). Some of the major questions being asked include what are the mechanisms behind extinction events and could humans possibly cause a mass extinction? One of the more recent extinctions in geologic time that may provide some insight into these questions is the Pleistocene megafaunal extinction that occurred in North America. Three hypotheses have been made on the cause of the Pleistocene extinction, which include: 1) vegetation and climate change, 2) over-hunting by humans, and 3) the introduction of disease brought into North America by humans, the last of which is known as the hyper-disease hypothesis (MacPhee and Marx 1997; Lyons et al. 2004). Continue reading
We are all familiar with the images. The barren landscape. Brown, dead vegetation spanning as far as the eye can see. Lakes and rivers shrinking in size, their relict banks cracked and dry.
These dryspells or droughts can last from days to years and they occur when a region receives below average precipitation. Droughts are generally said to arise from insufficient precipitation amounts over an extended period of time. This shortage in precipitation occurs typically in one season or more, and results in a water shortage for an environmental region. The impact of the drought arises from the interaction between the natural events (less precipitation than expected) and the demand on the water supply (both from the environment and humans), which can exacerbate the impacts of the drought. Because of these factors that can influence the magnitude of the drought, they need to be taken into consideration when working to define a drought (National Drought and Mitigation Center). Frequently the definitions can vary from location to location as certain areas are less adapted to low water conditions than others. But it can also dependent on timing. For example, in the desert a month without rain doesn’t have the same effect as it would in the rainforest. However, if the month without rain in the desert came during the period designated as the rainy season, the impacts would be drastically different.
Depending on how long these dryspells last there can be a huge impact on the ecosystem and economies associated with them. One prime example is the Dust Bowl. Continue reading