{"id":16047,"date":"2019-12-26T15:27:48","date_gmt":"2019-12-26T20:27:48","guid":{"rendered":"https:\/\/esa.org\/esablog\/?p=16047"},"modified":"2019-12-26T15:27:48","modified_gmt":"2019-12-26T20:27:48","slug":"silverswords-may-be-gone-with-the-wind-shifts-in-trade-winds-that-is","status":"publish","type":"post","link":"https:\/\/esa.org\/esablog\/2019\/12\/26\/silverswords-may-be-gone-with-the-wind-shifts-in-trade-winds-that-is\/","title":{"rendered":"Silverswords may be gone with the wind – shifts in trade winds, that is"},"content":{"rendered":"

A rare, iconic Hawai\u2019ian plant faces hardships as climate change affects trade winds<\/em><\/h3>\n

Silversword plants of Hawai\u2019i are unique to the Maui\u2019s Haleakal\u0101 volcano summit area and to the Mauna Kea and Mauna Loa volcanoes on the Big Island. Each volcanic mountain has its own unique type of silversword. The Haleakal\u0101 species \u2013 known by its Hawai\u2019ian name \u2018\u0101hinahina which translates to very grey \u2013 is highly threatened and is considered by many to be the most beautiful. But they are growing rarer due to drought, especially at lower elevations on the volcano slopes.<\/p>\n

\"\"<\/a>

Silverswords flowering at Haleakal\u0101 National Park, Maui, Hawaii. Photo courtesy of Forest and Kim Starr \/ CC BY 2.0.<\/em><\/p><\/div>\n

In a\u00a0new study<\/a>\u00a0in the Ecological Society of America\u2019s journal\u00a0Ecological Monographs,\u00a0<\/em>researchers seek to understand recent population declines of Haleakal\u0101 silverswords and identify conservation strategies for the future.<\/p>\n

\"\"<\/a>

Photo courtesy of Jean Beaufort.<\/em><\/p><\/div>\n

Because silverswords grow at high elevations between 5,000 and 10,000 feet, they have thoroughly adapted to the harsh environment there. These plants, with very dense rosettes of spiky leaves that radiate out from the base, produce towering blooms that can reach up to six feet high. The plants live from 15 to more than 50 years, but they bloom only once and die. Climate change imposes a new threat to these charismatic plants: hotter and drier conditions threaten even hardy silverswords.<\/p>\n

Researchers with the University of Hawai\u2019i are actively working with Haleakal\u0101 National Park staff to evaluate the effects of drought conditions on silverswords and to preserve these unique plants for generations to come.<\/p>\n

Paul Krushelnycky, a researcher with the University of Hawai\u2019i, and colleagues tracked growth of silversword plants for over three and a half years in greenhouse and out-planting experiments at the bottom, middle, and top of the plant\u2019s elevation range on Haleakal\u0101. They studied the adaptability of silverswords to environmental or climatic changes and they also studied the plants\u2019 genes to see if some plants have genes that help them withstand drought better than others.<\/p>\n

In the experiments, researchers found a counter-intuitive result, but one that is in line with what has been seen in the wild. \u201cPlants have been dying at greater rates in wetter portions of the range, in response to drying conditions, rather than in drier areas,\u201d says Krushelnycky. \u201cIt\u2019s contrary to the prediction that one would normally make \u2013 namely, that the population should shift towards wetter areas as conditions get drier.\u201d<\/p>\n

\"\"<\/a>

A silversword in Haleakal\u0101 in peak bloom. Photo courtesy of Forest and Kim Starr \/ CC BY 2.0.<\/em><\/p><\/div>\n

It appears that lower elevation plants are less drought-resistant than higher elevation plants, which are already living in a drier environment and are thus more adaptable to extra-stressful dry seasons. The plants at lower elevation are thus dying off more than their higher counterparts during recent dry seasons. This pattern may be enhanced by strong changes in typical climate conditions at lower elevations.<\/p>\n

One such change, and an extremely important factor for Hawai\u2019i volcano climate overall, is the frequency and elevation of the trade wind inversion (TWI). \u201cIt\u2019s the trade wind inversion, not the trade winds per se, that is important in creating the relevant ecotone high on the mountain,\u201d explains Krushelnycky. \u201cAbove the TWI, it\u2019s much drier and clearer most of the time, and this appears to be important in determining not just the lower boundary of silverswords, but also the boundaries of several plant communities on the mountain.\u201d<\/p>\n

An inversion is a layer in the atmosphere in which temperature increases, not decreases, with height, creating a kind of \u2018cap\u2019 of warm air. In Hawai\u2019i this commonly occurs at about 6,000 to 8,000 feet. The presence of the TWI influences many aspects of Hawai\u2019ian climate, including limiting cloud height, limiting the amount of rainfall on the islands, and producing dry air and clear skies at the highest elevations on volcanoes. Because the TWI limits how far air can rise, it plays a big part in how strong convective clouds and showers can become \u2013 a lower TWI elevation leads to lighter rainshowers or clouds with no showers at all.<\/p>\n

\"\"<\/a>

The top of inversion-layer clouds are seen from above here at Haleakal\u0101 National Park. Conditions above the layer are clearer and drier more consistently than below. Photo courtesy of Forest and Kim Starr \/ CC BY 2.0.<\/em><\/p><\/div>\n

The occurrence of the TWI has increased in recent decades, which leads to more persistent clear and dry \u2013 and thus stressful \u2013 conditions high on Haleakal\u0101. Kryschelnycky says some climate projections predict TWIs will be even more frequent in the future, and possibly at lower elevation. Both of these changes would lead to more of the silversword range being exposed to stressful conditions. All in all, the changing climate would jeopardize the plants\u2019 survival even more.<\/p>\n

The delicate silverswords, once ripped up and taken home by visitors as souvenirs before the creation of Haleakal\u0101 National Park, now depend on management efforts for survival. Park staff fence out predators, destroy non-native plants that would crowd out silverswords, and educate park visitors to stay on trails to avoid stepping on fragile silversword seedlings and root systems. As for future management, Krushelnycky believes efforts should focus on using suitable places for silverswords to live in the face of climate changes, rather than trying to find or breed the silverswords with particularly drought-resistant genes.<\/p>\n

\u201cThe study highlights how plant population responses to changing climate can be quite complex,\u201d says Krushelnycky, \u201cboth in terms of the underlying mechanisms and the outcomes.\u201d With continued study of silverswords and similarly-affected plants, the researchers think case studies like this will reveal more factors essential for consideration in broader conservation efforts.<\/p>\n

\"\"<\/a>

Photo courtesy of wikicommons.<\/em><\/p><\/div>\n

\u00a0<\/p>\n

\n

Journal article: Krushelnycky, Paul, et al. 2019. \u201cClinal variation in drought resistance shapes past population declines and future management of a threatened plant.\u201d\u00a0Ecological Monographs.<\/em>\u00a0DOI: 10.1002\/ecm.1398<\/a><\/p>\n

\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"

A rare, iconic Hawai\u2019ian plant faces hardships as climate change affects trade winds Silversword plants of Hawai\u2019i are unique to the Maui\u2019s Haleakal\u0101 volcano summit area and to the Mauna Kea and Mauna Loa volcanoes on the Big Island. Each volcanic mountain has its own unique type of silversword. The Haleakal\u0101 species \u2013 known by its Hawai\u2019ian name \u2018\u0101hinahina which…<\/p>\n","protected":false},"author":20,"featured_media":16057,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"class_list":["post-16047","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"_links":{"self":[{"href":"https:\/\/esa.org\/esablog\/wp-json\/wp\/v2\/posts\/16047","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/esa.org\/esablog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/esa.org\/esablog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/esa.org\/esablog\/wp-json\/wp\/v2\/users\/20"}],"replies":[{"embeddable":true,"href":"https:\/\/esa.org\/esablog\/wp-json\/wp\/v2\/comments?post=16047"}],"version-history":[{"count":0,"href":"https:\/\/esa.org\/esablog\/wp-json\/wp\/v2\/posts\/16047\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/esa.org\/esablog\/wp-json\/wp\/v2\/media\/16057"}],"wp:attachment":[{"href":"https:\/\/esa.org\/esablog\/wp-json\/wp\/v2\/media?parent=16047"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/esa.org\/esablog\/wp-json\/wp\/v2\/categories?post=16047"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/esa.org\/esablog\/wp-json\/wp\/v2\/tags?post=16047"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}