 Biodiversity is a variety of life, as we saw in this video. There are 4 to be 8.7 million species on planet Earth, and as we saw in this video, biodiversity is of utmost importance to humans. The loss of one key species can have a detrimental impact on many levels, from other species of animals to plants to the physical environment, as shown by wolves. Human activities are reducing biodiversity, our future depends upon maintaining a good level of biodiversity, and so we need to start taking measures to try and stop the reduction. In this video, we are going to look at how humans are negatively impacting biodiversity. Here are some of the main human-induced threats facing biodiversity. As the world population has grown from 1.5 billion in 1900 to nearly 7.5 billion people today, unsurprisingly the land use has changed. Habitants have been destroyed in favor of agriculture, forestry, fishing, urbanization and manufacturing. Unsurprisingly habitat loss has greatly reduced species richness. Habitat fragmentation has also meant that populations have been split into smaller subunits, which then when faced by challenging circumstances have not been able to adapt and survive. After habitat loss, over harvesting has had a huge effect on biodiversity. This has historically exploited plant and animal species for short-term profit. If a resource is profitable, we develop more efficient methods of harvesting it, inevitably depleting the resource. As is currently happening with fishing and logging, the exploited species needs protection. The difficulty is that the demand then outstrips the supply, and so the resource value rises. This increases the incentive to extract the resource, and leads to the final collapse of the population. As happened with whales, elephants, spotted cats, cod, tuna and many more species. Human activities are polluting the air and water. Toxics discharge into water from industrial processes unsurprisingly has a negative effect on local aquatic species by killing, weakening or affecting their ability to reproduce. Another big water pollution problem is eutropification, which we'll look at in detail in this video. Phosphorus and nitrogen infertilizes run off agricultural fields and pass into rivers. These surplus nutrients cause algae to bloom, which then starves other aquatic species of oxygen and light, causing them to die. Acid rain is the consequence of humans polluting the air. This causes lakes and water bodies to become more acidic, killing fish, molluscs, amphibians and many other species. A huge impact humans have had on planet earth is the introduction of alien species to habitats. In fact, it is estimated that on any given day there are 3,000 species in transit aboard ocean going vessels. Alien species can cause problems in a number of ways. Pause the video and have a look. Throughout the earth's history there have been periods of rapid climate change that have led to mass extinction events. We are currently in a period of fluctuating climate, but nearly all scientists agree that humans are activities like burning fossil fuels or speeding up global warming. We don't know how much climate change is going to affect biodiversity in the future, but it is predicted to be huge. Toss of sea ice and ocean acidification are already causing huge reductions in biodiversity. Climate change alters temperature and weather patterns, with changing patterns of rainfall and drought expected to have significant impacts on biodiversity. So there you have a selection of human related impacts on biodiversity. There are many more, which with a quick search on the internet will bring up. If you want to understand why we should care about maintaining biodiversity, watch this video.