Final answer:
A significant portion of Earth's land is affected by climate and human activities that render it less suitable or unsuitable for habitation, with 25% of agricultural land highly degraded and other areas inhospitable due to natural features.
Step-by-step explanation:
The impact of climate on habitability can be measured by considering various factors, such as the degradation of arable land and the accessibility of freshwater. According to the Food and Agricultural Organization (FAO), climate change is likely to exacerbate the degradation of agricultural land, with a quarter already highly degraded and an additional 8 percent moderately degraded. When combined with other types of uninhabitable areas, including deserts, high mountains, and polar regions, it is estimated that a significant portion of land is affected by harsh climatic conditions rendering them less suitable or unsuitable for human habitation. Furthermore, with the sea level rise potential from melting ice sheets and the progression of desertification, more regions may become uninhabitable or less viable for agriculture and human settlement in the future. While there is no specific percentage that encompasses all lands rendered uninhabitable solely by climate, it is clear that human activity's impact on the environment is a critical factor in land degradation and potential habitability.