1. Humans cannot reproduce the vast and complicated biodiversity of natural areas, so the first priority has to be preservation of those areas and removal of invasives. Even small patches of invasive plant species have cascading effects on the insect population of a much greater area around them. Removing those invasive plants does wonders for biodiversity.

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2. Where natural biodiversity has already been destroyed, humans can help by planting a wide variety of native species. You can’t prevent species extinctions by focusing on a single plant-pollinator interaction. You have to focus on the ecosystem as a whole. So add as many species of native plants as your growing conditions allow, and cram in as many plants as you can afford. Plan for a succession of blooms from early spring to late fall.

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About 80% of bees are plant generalists - they can forage on a wide variety of flowers. To support these bees, provide a succession of blooms from early spring to late fall. Use locally native plants that fit into the ecosystem.

 

About 20% of bee species are specialists, requiring certain plant species for their nectar and pollen. (An easy example is the Southeastern Blueberry Bee.) The life cycle of these bees is timed to the bloom time of their plants. (These bees may only live a week or two, which means that changes in bloom time because of climate change can threaten their survival. Intense heat is also problematic, as it can render them sterile.) One major determinant of which flowers they use is the shape of the bloom. For example, some bees have absurdly long tongues, others have short ones. All these bees (and their associated plants) are essential for a healthy ecosystem.These species are in decline and need our help the most. They are more susceptible to the effects of insecticides. 

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• Nectar: Adult bees use nectar for their own energy, and some bees are plant generalists. Many are specialists, though, requiring flowers of different shapes depending on the length of the bee’s tongue and other foraging factors.

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• Pollen: Not all pollen is the same. Bees get themselves covered with pollen accidentally and therefore help with pollination. But to feed their young, they need the pollen from specific plant species and seek it out deliberately, often “buzzing” the flowers to collect it. The population of many species of bees is limited by the availability of the right pollen. Native bees only live for a week or two, so timing is crucial. For those who have a lot of room, one strategy to provide needed food pollen from spring to late summer would be to plant native willows, native St. John’s Wort, Virginia Rose and Carolina Rose. 

 

The problem with non-native plants:

Even a small patch of non-native flowers may seriously distort the diversity of bee species in your garden. It is always best to stick to natives. Seeing a large number of bumblebee individuals in your yard does not necessarily mean you have created a healthy ecosystem. If you are trying to prevent the decline of threatened bee species, what counts is how many different bee species you are seeing.

 

The problem with insecticides:

Studies of the effect of pesticides on bees have focused on short term effects on those species that have immediate economic importance to human beings, namely the European honeybee and to a much lesser extent, the Common Eastern Bumblebee. Massive and heart-breaking die-offs of declining species of native bees is largely ignored, though studies have demonstrated that they are more susceptible to lower doses of insecticides.