Estimates of species loss are, without a doubt, staggering. In 2007, Sigmar Gabriel, the Federal Environment Minister of Germany, cited estimates that up to 30% of all species will be extinct by 2050. Others have estimated that as many as 140,000 species are lost each year. The alarming trends have led some to declare the current period the "Sixth Great Extinction."

But, extinctions—even mass extinction events—are not new. Though the current trend is caused, undeniably, by human action—through poaching, habitat destruction, pollution, and anthropogenic climate change, among others—mass reductions in biodiversity can—and have—occur without human interference.

The question then, is what does humanity lose when global biodiversity is significantly reduced?

Simply: A lot. Here are six significant human problems caused by reduced biodiversity:

1. Economic Cost of Lost Biodiversity

Treehugger / Christian Yonkers

Topping the list, of course, is the monetary value of biodiversity around the world. In terms of ecosystem services—functions like pollination, irrigation, soil reclamation, and other things that would have to be paid for if nature couldn't take care of it on its own—the value of global biodiversity has been estimated in the trillions. Because of this, deforestation alone has been estimated to cost between $2-5 trillion annually worldwide.

2. Reduced Food Security

Treehugger / Christian Yonkers

Reductions in biodiversity do not only occur during deforestation or through poaching. The introduction of new species is another culprit. These new species increase competition amongst locals and often lead to the extinction of native populations. In much of the world, this is happening on farms, too, where foreign breeds of cattle are being imported, pushing out natives.

This means that the world's livestock population is becoming increasingly narrow and more vulnerable to disease, drought, and changes in climate, leading to an overall reduction in food security.

3. Increased Contact With Disease

Treehugger / Christian Yonkers

The loss of biodiversity has two significant impacts on human health and the spread of disease. First, it increases the number of disease-carrying animals in local populations. Research has shown that the species best adapted to survive critically fragmented habitats are also the most prolific carriers of pathogens. As habitats are broken apart and reduced in size, these animals become more common, winning out over the species that do not typically transmit disease.

At the same time, habitat fragmentation brings humans in closer and more frequent contact with these disease-carrying species.

4. More Unpredictable Weather

Treehugger / Christian Yonkers

If forecasting the weather seems simply a matter of deciding to bring an umbrella or not, ask any farmer or coastal homeowner how they feel. Indeed, unseasonable weather, extreme weather, and weather that does not perform to historical norms is a huge problem that can lead to drought, destruction, and displacement.

The loss of species—even those replaced by invasives—has been shown to cause more unpredictable weather.

5. Loss of Livelihoods

Treehugger / Christian Yonkers

From fishermen to farmers, biodiversity—not to mention healthy ecosystems—is essential to maintaining livelihoods. When ocean ecosystems collapse, for example, entire communities built on the bounty they provide fold as well. Whether the cause is pollution, overfishing, ocean acidification, or a combination of these and more, humans are tied to the downfall of the ecosystems that surround them.

6. Losing Sight of "Nature"

Treehugger / Christian Yonkers

Beyond the utility of nature, of course, is the value of Nature to humanity. While an understanding of the science of the natural world does not diminish its grandeur, the physical deflation of it certainly does. When people finally look up from their desks and out their windows, will they be surprised by what remains?