This week the UN’s population division announced the 7 billionth human has been born.

Now 7 billion is a BIG number by any terms but just how does a population of 7 billion humans compare to other species and more importantly what does the size of our population mean for our planet?

We might begin putting these sorts of numbers in perspective by ranking the human population against others with a little help from wikipedia.

By far and away the most populous species on the planet are bacteria with numbers in the vicinity of 4 quadrillion quadrillion (4×1030) easily outnumbering all other animal populations combined. In the oceans there are an estimated 500 trillion krill, and while that is still an impressive number, their biomass is only around 50% of that of humans.

If we then move onto larger beings there are an estimated 10 billion billion ants in the world- (who counted them all?), with a combined biomass of almost 10 times that of humans. And who would have thought there are more than 20 billion domestic chickens wandering around providing humans with a significant source of their daily nutritional requirements?

Interestingly but not surprisingly the top ten mammalian populations are held exclusively by humans and their domesticated friends. As modern civilisation has allowed human populations to expand well beyond those of subsistence level, the associated agricultural production of livestock has seen populations of cattle (1.4 billion) and sheep (1.1 billion) far exceed what would be expected in wild ecological systems. Likewise, domesticated pets like cats and dogs are estimated to have populations of around 500 million each, due to their close association with humans.

But it becomes a little more controversial as to which species is actually number one. Although there is no real way of knowing, there is an over-riding body of evidence that would suggest that humans might be third on this list after mice and rats, which although not domesticated strictly speaking, have a liking for human’s domesticated lifestyles.

By comparison populations of non- domesticated large mammals struggle to get into the tens of millions and although kangaroos are highly successful at 60 million- most wild mammal populations are in the single millions or lower due to human encroachment on their habitat. Make no mistake, that when you see the population sizes of large terrestrial mammals falling (500 000 elephants, 200 000 chimpanzees, 120 000 for all big cat species and 20 000 polar bears), the growing human population is directly responsible for their decline.

So when it comes to numerical superiority humans are right up there, and we probably should be celebrating our success. But rather the tone this week has been somewhat circumspect. In general there seems to be some concern with the size of our (over) population and the challenges we now face on a global scale. Not the least of which is providing on going food security, not for the 7 billion people alive today, but the 9 billion people expected to inhabit the planet by 2050.

Most experts seem to think that feeding 10 billion people is well within the capacity of modern agriculture. However the major problem will be changing the attitudes of first world societies towards food. There will have to be a radical shift in thinking across a range of issues if we are to achieve food security for the global population. And of course providing safe drinking water for all these people is just as important an issue.

Then there is the question of other vital resources. Raw materials now are being mined at an ever increasing rate to feed an increasingly wasteful consumer economy. If global growth was to continue to rely these principles it would take 1.5 earths within 30 years just to keep up the supply. Perhaps its time for the whole world to have a serious look at making recycling part of our lives?

Powering our modern lifestyles is also proving to be a challenge for the future. Fossil fuels might have seemed infinite 100 years ago, but we have now discovered that there are only finite ways to access them. This once inexpensive and easily produced source of energy is now becoming more and more complicated in its supply and its cost. Add the fact we are now endangering important ecosystems and prime agricultural land to access it, is just another reason to transition away from it to more efficient sources like nuclear, solar and geothermal.

So its no wonder the 7 billion celebration was muted- especially when the problems our species face are mainly of our own making. Yet, perhaps we should tackle these problems with a sense of optimism- overcoming them is represents a challenge that might finally unite all of humanity. As a species humans have notched some pretty impressive achievements along the journey. After all, it was our oversized brains that got us into this situation, and if we put the collective mental capacity of 7 billion people to the task, not only will we solve these problems but we might even make the world a better place.

Steve discusses this topic along with co-host Ben Warner in “FiST Chat” episode POPULATION: 7 BILLION.