Do threats to biodiversity pose the greatest challenge to humanity for the 21st century?

Introduction:
The term biodiversity refers to the variety of life on Earth at all its levels, from genes to ecosystems, and the ecological and evolutionary processes that sustain it. Biodiversity includes not only special we consider rare, threatened, or endangered, but every living thing even organisms we still know little about, such as microbes, fungi, and invertebrates. Biodiversity is important everywhere; species and habitats in your area as well as those in distant lands all play a role in maintaining healthy ecosystems.
Biodiversity is important because it boosts ecosystem productivity where each species, no matter how small, all have an important role to play. For example, a larger number of plant species means a greater variety of crops. Greater species diversity ensures natural sustainability for all life forms.
There are five main threats to biodiversity that I can cover later on in this report are: 1. Invasive alien species 2. Climate change 3. Nutrient loading 4. Water pollution 5. Loss of habitat 6. Overexploitation
In this report my goal is to explain what biodiversity is in detail in depth and explain how important it is to the world. Also, to outline if and how these threats pose a threat to humanity in the 21st century.
How important is biodiversity?
Biodiversity is important for all species' survival. We need a variety of habitats for all the different species because each species is adapted to a certain set of environmental conditions. All species depend on each other to survive, so if one becomes extinct another species that relies on it could go extinct as well. Individual traits can allow some species to adapt to environmental changes, but many species cannot adapt if their habitat and food chains are greatly altered.
The threats Invasive alien species have devastating impacts on native biota, causing decline or even extinctions of native species, and negatively affecting ecosystems. Invasive alien species are animals, plants, fungi and microorganisms entered and established in the environment from outside of their natural habitat. They reproduce rapidly, out-compete native species for food, water and space, and are one of the main causes of global biodiversity loss. Species are often introduced deliberately, through for example, fish farming, pet trade, horticulture, and bio control; or unintentionally, through such means as land and water transportation, travel, and scientific research.
The threats:
Loss of habitat
Loss of habitat is an important cause of known extinctions and is considered by conservation biologists to be the primary cause of biodiversity loss. As deforestation proceeds in tropical forests, this comes closer and closer to becoming the highest mass extinction caused by human activity.
All species have specific food and habitat needs. The more specific these needs and localised the habitat, the greater the vulnerability of species to loss of habitat to agricultural land, livestock, roads and cities. In the future, the only species that survive are likely to be those whose habitats are highly protected, or whose habitat corresponds to the degraded state associated with human activity.
Habitat damage, especially the conversion of forested land to agriculture (and, often, subsequent abandonment as marginal land), has a long human history. It began in China about 4,000 years ago, also largely completed in Europe by about 400 years ago, and swept across USA over the past 200 years.
Habitat loss is a huge issue when it comes to tropical forests because they harbour at least 50%, and perhaps more, of the world's biodiversity. Humans as a species are playing a huge part when it comes to habitat loss in these types of areas, the original extent of tropical rain forests was 15 million km2. Now there remains about 7.5-8 million km2, so half is gone. And this is mainly due to deforestation which is still a threat in today’s world even though we know the consequences but it has slowed down.

In November Brazil announced deforestation rates in the Amazon declined 27 percent from August 2011 to July 2012, reaching the lowest rates ever recorded for the fourth consecutive year.
According to Brazil’s National Institute for Space Research (INPE), 4656 square kilometres of Amazon rainforest were cleared over the twelve months, compared with 27,772 square kilometres in 2004.
Brazil’s government says this represents a 76 percent reduction since 2004 – coming close to the country’s commitment to reduce deforestation in the Amazon region 80 percent by 2020.
Lastly Clearance of native vegetation for agriculture, housing, timber and industry, as well as draining wetlands and flooding valleys to form reservoirs, destroys these habitats and all the organisms in them. In addition, this destruction can cause remaining habitats to become fragmented and so too small for some organisms to persist, or fragments may be too far apart for other organisms to move between.
Invasive alien species
Invasive alien species are the second greatest threat to biodiversity worldwide. Whether introduced on purpose or accidentally, non-native species can cause severe problems in the ecosystems they invade, from affecting individuals to causing huge changes in ecosystem functioning and the extinction of many species. Virtually all ecosystems worldwide have suffered invasion by the main taxonomic groups. This problem will probably get worse during the next century driven by climate change, and an increase in global trade and tourism. As well as the risks to human health, alien species inflict massive economic costs to agriculture, forestry, fisheries and other human activities.

Nutrient loading
All forms of pollution pose a serious threat to biodiversity, but in particular nutrient loading, primarily of nitrogen and phosphorus, which is a major and increasing cause of biodiversity loss and ecosystem dysfunction. Atmospheric nitrogen deposition represents a major threat to European biodiversity and a serious challenge for the conservation of natural habitats and species. In addition, nitrogen compounds can lead to eutrophication of ecosystems. The main pollution sources are from transport and agriculture. It is the only air pollutant for which concentrations have not decreased in Europe following the implementation of legislation.
For many European ecosystem types, studies have concluded that nitrogen deposition results in loss of species richness. Peat land ecosystems provide an example of how species replacement, resulting from nitrogen deposition, may alter ecosystems functionality. For example, the carbon sequestration capacity of rain fed (ombrotrophic) bog ecosystems decreases when subjected to elevated nitrogen inputs.