Having said that, I do agree that it is unavoidable to have increasing prices on oil, in an attempt to slow the rate of depletion of this resource that is not unlimited.

slow 在这里是动词，意思是"使变慢、减缓"。这个词的基本含义是指降低速度或延缓进程。在句中，slow 作为动词使用，表示通过提高油价来"减缓"资源耗尽的速度。