Mae'r Rheoliadau'n pennu trothwyon sy'n diffinio'r pwynt lle bydd prosiectau plannu neu goedwigo newydd yn debygol o gael effaith arwyddocaol ac y bydd angen caniatâd arnynt. Fel arfer, ond nid bob tro, os yw prosiect o dan y trothwy perthnasol, credir na fydd yn debygol o gael effaith arwyddocaol. Mae prosiectau uwchlaw'r trothwyon hyn yn cael eu hystyried (“sgrinio”) gan CNC a fydd yn penderfynu a oes angen cynnal EIA llawn neu beidio. Dyma'r trothwyon presennol: 5 hectar mewn ardal nad yw'n sensitif, 2 hectar mewn ardal sensitif fel Parc Cenedlaethol neu Ardal o Harddwch Naturiol Eithriadol; a sero yn yr ardaloedd mwyaf sensitif, fel Safleoedd o Ddiddordeb Gwyddonol Arbennig. Mae’n bosibl y bydd yn rhaid parhau i dderbyn caniatád ar gyfer prosiectau sydd o dan y trothwy perthnasol os ydy CNC o’r farn, er gwaethaf y ffaith eu bod yn brosiectau bychain (er enghraifft ble y maent yn agos at gynefin arbennig o sensitif) maent yn debygol o gael effaith arwyddocaol ar yr amgylchedd.
The Regulations operate thresholds to define the point at which new planting, or afforestation, projects are likely to have a significant effect and require consent.  Generally a project below the relevant threshold may be considered as not likely to have significant effects.  Projects above the threshold are considered (“screened”) by NRW who will decide whether or not a full EIA must be undertaken.  The current thresholds are:  5 hectares in non-sensitive areas, 2 hectares in sensitive areas such as National Parks and Areas of Outstanding Natural Beauty; and zero in the most sensitive areas such as Sites of Special Scientific Interest.  Projects below the threshold may still require consent where NRW considers that despite their small size, (for example where they are close to a particularly sensitive habitat) they are likely to have significant effects on the environment.