The implications of climate change can reverberate through ecosystems, wreaking havoc on the delicate interactions that have evolved between species over millions of years.
In western North America, the relationship between the glacier lily and the broad-tailed hummingbird is in danger. The plant flowers in early spring, when the first hummingbirds arrive. Or at least it used to. A new study by AAAS member David Inouye and Amy McKinney of the University of Maryland and colleagues shows the lily's first blooms are appearing two to three weeks earlier than they did forty years ago. The timing of these first blooms is no longer synchronized with the arrival of the hummingbirds, who depend on the lilies for nectar.
AAASMC recently talked to Inouye about what this means for broad-tailed hummingbirds, glacier lilies, and other species threatened by our changing climate.
AAASMC: Can you explain the relationship between glacier lilies and broad-tailed hummingbird? Why is timing (of blooming and migration) especially important?
Professor David Inouye, University of Maryland: Glacier lilies are the second species to bloom after the snow melts at our study sites, and the Broad-tailed Hummingbirds visit them for nectar when they arrive from their winter grounds in Central America. Changes in the phenology (seasonal timing) of migration and of flowering are one of the best ways to measure the ecological consequences of the changing climate. Given the scarcity of other floral resources early in the season, the glacier lily (and then larkspur) is an important component of the hummingbirds' diet.
AAASMC: You and your colleagues found that the time between the first hummingbird and the first bloom has collapsed by 13 days over the past 40 years. Is this a dramatic change? How could this affect the hummingbirds?
Inouye: Yes, 13 days is a significant portion of the flowering period for most of the high-altitude wildflowers, so that is a dramatic change. If this trend continues, the hummingbirds will arrive at their summer breeding grounds after one of the important nectar resources they now utilize is already finished flowering. In addition to this, Broad-tailed Hummingbird reproduction is synchronized closely with peak floral abundance of the later important nectar resource: larkspur (Delphinium nuttallianum). As stated above, if hummingbirds continue to arrive later into the flowering season, the timing of their reproduction may be mistimed (i.e., later) with peak floral abundance of the larkspur, resulting in fewer offspring.
AAASMC: In the paper, you say that the asynchrony between lilies and hummingbirds is more problematic in more northern climates. Why is that?
Inouye: Higher latitudes and higher altitudes are experiencing stronger and more rapid consequences of climate change than other areas, especially at lower latitudes and elevations. Our study site at 9,500 feet in the Colorado Rocky Mountains does seem to be characteristic of that pattern. These hummingbirds began their migration from Central America based on lower-latitude seasonal cues. Because the effects of climate change are occurring at a faster rate at higher latitudes compared to lower latitudes, hummingbirds do not appear to have much of a problem with the timing of food resources along the lower-latitude portions of their migration route, but arrive later at northern breeding grounds, after important early season flowers have already started to bloom. In this case, arriving later in Colorado may have strong consequences.
AAASMC: Do you think the hummingbirds will be able to adapt to this consequence of climate change?
Inouye: It's possible that hummingbirds could learn to change the timing of their migration, and that they could learn to use additional floral resources. But as the growing season is getting longer, it seems that a mid-summer period of low floral resources is developing, which will also challenge the ability of hummingbirds at this high-altitude site to reproduce.
AAASMC: Could a disruption to the hummingbird-glacier lily relationship have more far-reaching implications in the ecosystem?
Inouye: The hummingbirds are important pollinators of several species of flowers that are not usually visited by other pollinators, so for those species, and for the animals that depend on them as herbivores or seed predators, there would be significant consequences if the hummingbirds decline in abundance.
Madhara ya mabadiliko ya hali ya hewa yanaweza kuenea katika mifumo ya ikolojia, na kusababisha uharibifu kwenye mwingiliano dhaifu ambao umebadilika kati ya spishi kwa mamilioni ya miaka. Katika sehemu ya magharibi ya Amerika Kaskazini, uhusiano kati ya maua ya mviringo na ndege anayeitwa broad-tailed hummingbird uko hatarini. Mti huo huchanua maua mapema katika majira ya kuchipua, wakati ndege wa kwanza wa aina ya hummingbird wanapowasili. Au angalau ilifanywa hivyo. Utafiti wa hivi karibuni uliofanywa na David Inouye na Amy McKinney, wanachama wa AAAS, na wenzake, unaonyesha maua ya kwanza ya lily yanaonekana wiki mbili hadi tatu mapema kuliko ilivyokuwa miaka 40 iliyopita. Wakati wa maua hayo ya kwanza haupatikani tena kwa wakati uleule wakati ndege hao wanaokuja, ambao hutegemea maua hayo kupata nectar. AAASMC hivi karibuni ilizungumza na Inouye juu ya nini hii inamaanisha kwa ndege wa mkia pana, maua ya mawe, na spishi zingine zinazotishiwa na mabadiliko yetu ya hali ya hewa. "Kama unavyojua, kuna uhusiano kati ya ""glassier lilies"" na ndege anayeitwa ""broad-tailed hummingbird.""" Kwa nini wakati (wa maua na uhamiaji) ni muhimu hasa? "Profesa David Inouye, Chuo Kikuu cha Maryland: ""Michungwa ya barafu ni spishi ya pili ya maua baada ya theluji kuyeyuka katika maeneo yetu ya utafiti, na ndege wa mkia pana huwatembelea kwa nectar wanapowasili kutoka maeneo yao ya majira ya baridi kali katika Amerika ya Kati." Mabadiliko katika phenology (wakati wa msimu) wa uhamiaji na maua ni moja ya njia bora ya kupima matokeo ya ikolojia ya mabadiliko ya hali ya hewa. Kwa sababu ya upungufu wa mimea mingine mapema katika msimu huo, maua ya mti wa mto (na baadaye ya mti wa mti wa mto) ni sehemu muhimu ya mlo wa ndege hao. "Mwanasayansi huyo alisema: ""Wakati kati ya kukua kwa ndege wa kwanza na kuota kwa maua ya kwanza umepungua kwa siku 13 katika miaka 40 iliyopita." Je, hilo ni badiliko kubwa? Hilo laweza kuwaathirije ndege hao? "Mwanamke mmoja alisema: ""Mwaka wa 13 ni kipindi kizuri sana cha maua kwa maua ya mwituni ya maeneo ya juu, kwa hiyo ni mabadiliko makubwa." Ikiwa hali hiyo itaendelea, ndege hao wa aina ya hummingbird watarudi kwenye maeneo yao ya majira ya kiangazi baada ya mojawapo ya vyanzo muhimu vya maji ya maua wanavyotumia sasa kumalizika. Kwa kuongezea, uzazi wa ndege anayeitwa Broad-tailed Hummingbird unalingana sana na upeo wa maua ya mimea muhimu ya baadaye: larkspur (Delphinium nuttallianum). Kama ilivyoelezwa hapo juu, ikiwa ndege wa hummingbird wanaendelea kufika baadaye katika msimu wa maua, wakati wa uzazi wao unaweza kuwa mbaya (yaani, baadaye) na wingi wa maua ya kilele cha larkspur, na kusababisha watoto wachache. "Kama ilivyoelezwa katika makala hii, ""Asynchrony kati ya lilies na hummingbirds ni zaidi ya tatizo katika hali ya hewa zaidi kaskazini.""" Kwa nini hilo? Inouye: Latitudo za juu na urefu wa juu zinakabiliwa na athari kali na za haraka za mabadiliko ya hali ya hewa kuliko maeneo mengine, haswa katika latitudo za chini na urefu. Kwa mfano, eneo la utafiti wa juu zaidi la Colorado, kwenye milima ya Rocky, linaonekana kuwa na mwelekeo wa kawaida. Ndege hao walianza kuhamia kutoka Amerika ya Kati kwa kutegemea misimu ya chini ya usawa. Kwa sababu athari za mabadiliko ya hali ya hewa zinatokea kwa kasi zaidi katika latitudo za juu ikilinganishwa na latitudo za chini, ndege wa hummingbird hawaonekani kuwa na shida kubwa na wakati wa rasilimali za chakula kwenye sehemu za latitudo za chini za njia yao ya uhamiaji, lakini hufika baadaye kwenye maeneo ya kaskazini ya kuzaliana, baada ya maua muhimu ya msimu wa mapema kuanza kuota. Katika kisa hiki, kufika Colorado baadaye kunaweza kuwa na matokeo mabaya. Je, unafikiri ndege hao wataweza kukabiliana na mabadiliko ya hali ya hewa? Inouye: Inawezekana kwamba ndege wa aina ya hummingbird wanaweza kujifunza kubadilisha wakati wa kuhamia kwao, na kwamba wanaweza kujifunza kutumia rasilimali za ziada za maua. Lakini kwa kuwa msimu wa kukua unazidi kuwa mrefu, inaonekana kwamba kipindi cha katikati ya majira ya joto cha rasilimali za maua ya chini kinakua, ambayo pia itapinga uwezo wa ndege wa hummingbird katika tovuti hii ya urefu wa juu kuzaliana. Je, kuharibika kwa uhusiano kati ya ndege wa hummingbird na lily ya barafu kunaweza kuwa na athari kubwa zaidi katika mazingira? Inouye ni pollinator muhimu wa aina kadhaa za maua ambayo kwa kawaida haitembelewa na pollinators nyingine, kwa hivyo kwa spishi hizo, na kwa wanyama wanaotegemea wao kama wadudu wa mimea au wavuvi wa mbegu, kutakuwa na matokeo makubwa ikiwa idadi ya hummingbirds itapungua.