The last century was one of incredible social changes and development. Improvements in health, urbanization, better education and industrialization has brought about economic growth and improved standards of living to much of the globe.
Yet, this progresses however, has been uneven leaving one million people still living in extreme poverty and has been accompanied by demographic and environmental change. Over the last hundred years, the population of the world has grown from around 1 billion peoples to more than 7 billion people. Human activity has transformed vast areas of the earth's surface, alerted the atmosphere resulted in thousands of plant and animal species extinctions.
Yes, population explosion matters for various reasons, the major one is it is a major contributor to resource scarcity. Others accessories impact follow one another, i.e. altering the climate, degrading habitats, overexploiting resources, and reducing biodiversity.
High fertility usually implies rapid population growth. This typically lowers the rate of growth of per capita income and, in addition, has serious consequences for the distribution of income across different classes of people. The growth in per capita income is downsized partly because some production inputs, such as agricultural land, are fixed in supply. Higher populations would mean that each agricultural worker, now having less land to work on, is less productive. And lower productivity implies lower per capita income.