Pumpkin puree, most frequently used to make pumpkin pies during the holidays, can also serve as an egg substitute in baked goods. It works especially well in dense, moist items, such as sweet breads and muffins. Trade 1/4 cup of pumpkin puree for each egg in the recipe.
Our Earth is also considered as an ecosystem on a much larger scale. When we introduce external factors such as too much carbon dioxide or methane, it destroys the balance of the ecosystem which in turn affects those who live in it. The result is global warming, water shortage, extinction of species, etc. These impacts every living thing on the planet, which includes us.
There are two impacts to the concept of supplying a limiting  nutrient to an ecosystem. The first is negative, when a nutrient  that is currently limiting algal growth (usually nitrogen or  phosphorus) is added to a body of water, you get an algal bloom or  red tide.