• World Over-Population:  Already, there are many areas around the planet that can not sustain the human populations, resulting in starvation, poverty, disease, crime, war, economic instability, pain and misery.  The world population is currently growing at an amazing 235,000 people per day (as of year 2018; that's 85.8 million per year; or about 1 billion per 11.6 years; that's all births minus all deaths per day)!

• Arable Land and Population:  Here's something to think about (with regard to population and arable land) and the impact on the  environment.  
  
  The Earth's Diameter is 7926.41 miles.
  
  The surface area of Earth is  (pi  x  Diameter²) = 197.38 million square miles (where pi = 3.14159265358979 ).
  
  However, the Earth only has 57 million square miles of land (that's 36.48 billion acres; there are 640 acres per square mile).
  However, there are only 12 million square miles (7.68 billion acres) of arable land.

The world population in year 1 A.D. was 250 million people.

The world population in year 1492 was 500 million people.

The world population in 1804 was 1.0 billion people.

The world population in 1922 was 2.0 billion people (increased by 1.0 billion in 118 years; increasing on average by about 23,000 per day).

The world population in 1959 was 3.0 billion people (increased by  1.0 billion in only 37  years; increasing on average by about 74,000 per day).

The world population in 2006 was 6.68 billion people (more than doubled in 47 years; increasing now by 211,000 people per day!).
 
The world population in 2018 was 7.71 billion people (increased by 1.0 billion in only 12 years; increasing by 235,000 people per day as of 2018!).
 
The world population by 2045 could be 15+ billion (only 27 years from 2018).

In 1959, there were 12.16 acres per person, world-wide (i.e. 36.48 billion acres / 3 billion people).
In 2006, there were 5.46 acres per person, world-wide (i.e. 36.48 billion acres / 6.68 billion people).
By 2039, there may be only 2.81 acres per person, world-wide (i.e. 36.48 billion acres / 13 billion people).

The U.S. has 3.794 million square miles, of which 3.54 million square miles is land area (for the U.S. population of 300 Million people as of the end of year 2006).
That is only 8.09 acres per person in the U.S.
However, only about a quarter of that is arable land.
That means there are only about 2.02 acres per person of arable land in the U.S.

However, consider that there is only 12 million square miles (7.68 billion acres) of arable land on the planet.
And, ignore for a moment that arable land is being lost at a rate of 38,610 square miles per year.
That is, lets assume no arable land is being lost for the next 33 years.  Then . . .

In 2006, there was 1.15 acres of arable land per person, world-wide (i.e. 7.68 billion acres / 6.68 billion people).
By 2039, there may be only 0.59 acres of arable land per person, world-wide (i.e. 7.68 billion acres / 13 billion people).
 
However, arable land is being lost at the alarming rate of over 38,610 square miles (24.7 million acres) per year.
Therefore, by  2039, there may be only 0.53 acres of arable land per person, world-wide (i.e. 6.865 billion acres / 13 billion people).
At the current rate of loss of 38,610 square miles per year of arable land, and even if the population didn't grow any larger, ALL arable land could be lost in only 310 years (12 million square miles / 38,610 square miles per year)!