fewer than 50 the number of officers engaged in search and rescue activities along the southern border. (g) U.S. Customs and Border Protection tunnel detection and technology program Not later than September 30, 2021, the Commissioner shall increase by not fewer than 50 the number of officers assisting task forces and activities related to deployment and operation of border tunnel detection technology and apprehensions of individuals using such tunnels for crossing into the United States, drug trafficking, or human smuggling. (h) Agricultural specialists Not later than September 30, 2021, the Secretary shall hire, train, and assign to duty, in addition to the officers and agents authorized under subsections (a) through (g), 631 U.S. Customs and Border Protection agricultural specialists to ports of entry along the southern border and the northern border. (i) GAO report If the staffing levels required under this section are not achieved by September 30, 2021, the Comptroller General of the United States shall conduct a review of the reasons why such levels were not achieved. 132. U.S. Customs and Border Protection retention incentives (a) Definitions In this section: (1) Covered area The term covered area means a geographic area that the Secretary determines is in a remote location or is an area for which it is difficult to find full-time permanent covered CBP employees, as compared to other ports of entry or Border Patrol sectors. (2) Covered CBP employee The term covered CBP employee means an employee of U.S. Customs and Border Protection performing activities that are critical to border security or customs enforcement, as determined by the Commissioner. (3) Rate of basic pay The term rate of basic pay — (A) means the rate of pay fixed by law or administrative action for the position to which an employee is appointed before deductions and including any special rate under subpart C of part 530 of title 5, Code of Federal Regulations, or similar payment under other legal authority, and any locality-based