This argument fails to take into account the costs of protecting endangered species and weigh them against the potential harms of them becoming extinct. In a world where only 5% of plant species have been surveyed for their potential medicinal value, [1] this means protecting the survival of the other 95% purely for the potential value that only a fraction of them may possess. All of this means denying development human development now, by not opening areas up for agriculture or not constructing housing. These are very real costs which impact upon peoples' lives, and may even outweigh those scientific and medical advances which may or may not be found in currently endangered species.  [1] Kurpis, Lauren. “Why Save?” EndangeredSpecie.com. Copyright 1997-2002.