Many countries, including China, have increased new areas of mangrove plantations to reverse the decline in mangrove ecosystem functions. However, this has led to the intrusion of mangroves into many tidal flat areas, which are important habitats for shorebirds. A reduction in the available tidal flat areas will reduce the diversity of shorebirds, therefore bringing mangrove conservation into conflict with shorebird conservation. In fact, a certain area of mangroves is an indispensable element of shorebird habitat. Therefore, this study proposes the maintenance of a ratio between the area of tidal flats and the area of mangroves within a mangrove ecosystem which is optimal for both mangrove conservation and shorebird conservation. This study recorded data for shorebird distribution, areas of mangrove and tidal flats, and other relevant data for Guangdong Province, China. The ratios of tidal flat areas to mangrove areas within mangrove ecosystems were established and a mathematical model was applied to establish the relationship between shorebird diversity and abundance and the ratios of tidal flat areas to mangrove areas. The results showed that: (1) there was no significant correlation between mangrove area and shorebird richness (r = 0.176, p = 0.230)and abundance(r = 0.104,p = 0.481), whereas there was no significant correlation between tidal flat area and shorebird richness(r = 0.153, p = 0.299)and abundance(r = −0.063,p = 0.670); (2) the relationship between the ratios of tidal flats area to mangrove area [x] and shorebird richness [f(x)] and abundance [g(x)] satisfied the cubic function equation f(x) = $0.106x^3-2.147x^2+11.269x$(0.0265≤x ≤ 13.8100) (R² = 0.714, P = 0.000),$g(x)=0.008x^3-0.189x^2+1.124x$ (0.0265≤ x ≤ 13.8100) (R² = 0.713, P = 0.000); (3) the appropriate value of x is 3.5662or 3.9785, and maintaining this ratio can reduce the conflict between mangrove conservation and shorebird conservation and promote the sustainable development of the mangrove ecosystem. This information can contribute to the sustainable development of mangrove planting management strategies at various scales and will be invaluable in assessing the effectiveness of existing mangrove management approaches.