A cоnservаtiоn оrgаnizаtion must decide whether to purchase and protect a 5,000-acre forest wilderness tract. The land contains healthy populations of common species but no endangered species. A developer offers to buy the same tract and has promised to develop only 30% of it, leaving 70% as "preserved green space" with walking trails and landscaped parks.Our author discusses several reasons for species preservation. Which of these most strongly supports buying the tract for full protection rather than accepting the developer's compromise?