Baishuidai Forest Park can be said to be the "green lung" of Jiangmen City. The following statements are incorrect: (a) The whole park is an ecosystem.

A. Ecosystem refers to the unified whole formed by organisms and environment in a certain area. It includes biological part and abiotic part. The biological part includes plants, animals, bacteria and fungi, and the abiotic part includes sunlight, air, water, soil and temperature, so the whole park is an ecosystem. A is correct;

B, under normal circumstances, the number and proportion of various organisms in the ecosystem is relatively stable. This shows that the ecosystem has certain automatic adjustment ability, but this adjustment ability is limited. When the interference of external factors exceeds this limit, the ecosystem will be destroyed. Therefore, the number and species of all wild animals and plants in the park will not increase indefinitely, B is wrong;

C. plants in the forest can absorb a lot of carbon dioxide and purify the air. C is correct;

D. Walking in the forest park in summer, the temperature in the forest is lower than that in the city center, because the transpiration of plants in the forest takes away some heat. D is correct.

Therefore, choose: B.