Driving along Highway 70 today, there were swaths of daffodils and tulips in bloom, groves of pear trees budding out and a warm breeze gave off that soft, earthy smell that signals spring has arrived. I should have been elated that winter was on the way out, but I wasn’t. March 4th is at least two weeks too early for springtime in our part of the Midwest.
Unfortunately, this year’s early spring isn’t an anomaly; results of global warming are not just causing seasons to shift, but are also throwing annual cycles, or phenophases, of all types out of sync. Leaf budding, plants flowering, insects emerging, birds and fish migrating are all showing signs of change. While they may seem insignificant on the surface – what difference can a week or two make for the start of spring? – the changes taking place in our environment are actually initiating some life altering scenarios for countless species, including humans.
In order to understand the implications of the disconnects in the natural world, one must first understand not only the connections that link plant and animal species together, (Remember using string to build the web of life in elementary school science – and the disappointment when the web fell apart because the string was cut?) but also how abiotic, or non-living factors, impact plants, animals and us. Average temperature changes, shifts in the rates, timing or amounts of precipitation, increases or decreases in the amount of sunlight, all abiotic components, can and do contribute to mismatches of the natural world’s annual cycles.
It’s common knowledge that plants are the foundation of the food chain. It follows then, that any changes to a plant’s life cycle will likely cause repercussions throughout the ecosystem. Plants are sprouting, budding, flowering and wilting weeks earlier than in previous decades. Insects however, are not keeping pace with the changes in plant life cycles. Research from the University of Oxford showed that “plants were found to be adjusting their seasonal timings four times faster than insects…” Data from another long term study in Europe showed that “60% of herbivorous insects are already struggling to keep up with plants they rely on…” Studies here in the United States echo the findings.
Over time, species of plants and insects have evolved so that they support one another. When insects are seeking nectar and pollen on which to feed, the flowers they need are in full bloom, with adequate nectar in their nectaries at the base of their stamens. At the same time, grains of pollen line their anthers ready to be transported by pollinating insects to other, nearby blooms. The nourished insects can go on to fulfill insect duties and the flowers can produce seeds and proliferate. The needs of both plant and animal are fulfilled.
If the phenophases are out of sync, if, for example, a flower produces all its blooms before its pollinator has developed from an egg to a larva to an adult, then both the flower and the insect will suffer. Without an adequate food source, the insect will become weakened. In its depleted state, reproduction is at risk. Either fewer eggs will be laid or more insects will die before they can reach maturity. In any case, a species is at risk.
At the same time, a reduced, or extinct, insect species impacts flower production. It’s notably dangerous for specialist plants and insects– those with a one-to-one relationship. Without their pollinators to spread grains of pollen, the plant will eventually begin to die out. Other species, especially robust invasives, will encroach on the space and take over.
The problem is that it isn’t just flowers in the garden that could be impacted by this disconnect. Over a third of global food production, or 80 - 85% of commercial crops, are pollinated by insects, with many in a one-to-one relationship. Without efficient pollination, food supplies could drastically dwindle, forcing many people into food deprivation.
This disconnect between plants and insects spills over into the animal kingdom as well. Many smaller mammals, such as mice and voles, rely on seeds, berries, tubers and other plant material as their food sources. If the vegetation disappears because of insect (pollination) decline, then the small animal population will also decline. Fewer mice and voles sounds like a boon for gardeners, until it becomes apparent that their predators – snakes, foxes and hawks, to name just a few, are also losing their food sources.
Birds too, are being impacted by the phenological shifts that are taking place. In the natural cycle, the migratory patterns of birds correspond to the availability of insects. Once migratory birds reach their nesting grounds, they require an enormous amount of nutrient dense food, insects, to re-energize themselves after their flights and to feed their hatching chicks. Many species of migratory birds, particularly short distance fliers, are arriving early before their insect buffets are ready. Inadequate food sources leave both adult and baby birds in danger of starvation and death. Without birds to control insect populations, humans may find insect-borne diseases like Lyme disease and malaria on the rise.
So much of my joy in life these days comes from spending time in nature with my grandchildren. I love watching them discover the first snowdrops of the season or seeing a newly arrived robin carrying a worm away to its nest. I wonder though, if years from now, they will be able to share the same moments with their grandchildren. While sometimes it feels like I am powerless to change the direction our world is headed, the reality is that there are things that individuals can do to help heal our planet. Join us next week as we explore the opportunities we each have to keep our world in sync.