It is not just the lions that are threatened. Elephants, tigers, many or the remaining large cats, all may be extinct within another 100 years.
We are in the Anthropocene era now, the age of anthropogenic impacts on our world, whether we want to admit it, or not. It is not just the weather we are profoundly altering with our growth in population and our activities which alter the ecology and environment.
We are also altering and decreasing the balance of species diversity, namely be creating conditions world wide that are wiping species out at a rate that is the greatest since the end of the dinosaurs. This accelerated extinction rate has been ramping up through the Holocene. Quoting from summary in Wikipedia:
The Holocene extinction, sometimes called the Sixth Extinction, is a name proposed to describe the extinction event of species that has occurred during the present Holocene epoch (since around 10,000 BC). The large number of extinctions span numerous families of plants and animals including mammals, birds, amphibians, reptiles and arthropods. Although 875 extinctions occurring between 1500 and 2009 have been documented by the International Union for Conservation of Nature and Natural Resources, the vast majority are undocumented. According to the species-area theory and based on upper-bound estimating, the present rate of extinction may be up to 140,000 species per year.
The Holocene extinction includes the disappearance of large mammals known as megafauna, starting between 9,000 and 13,000 years ago, the end of the last Ice Age. This may have been due to the extinction of the mammoth that had maintained grasslands that became birch forests without the mammoths. The new forest and the resulting forest fires may have induced climate change. Such disappearances might be the result of the proliferation of modern humans which led to climate change. These extinctions, occurring near the Pleistocene–Holocene boundary, are sometimes referred to as the Quaternary extinction event. The Holocene extinction continues into the 21st century.