Why are new copper extraction methods needed as high-grade copper ores become scarce?

New copper extraction methods are needed because high-grade copper ores, which contain a higher concentration of copper, are being depleted. As these ores become less available, it is essential to develop alternative methods, such as phytomining and bioleaching, to extract copper from lower-grade ores more efficiently and sustainably.

A strong answer should directly address the approved learning objective to explain why new copper extraction methods are needed as high-grade copper ores become scarce. (HT only). This question belongs to Alternative methods of extracting metals within Using the Earth's resources and obtaining potable water, so the response should use that exact curriculum context rather than a generic statement. The answer is correct when it names the key idea, explains the link to HT only, and keeps the wording specific to AQA GCSE revision.