Aquecimento global ameaça a produção agrícola da Califórnia

[Por Henrique Cortez, do EcoDebate] Já se sabe que as mudanças climáticas e o aquecimento global terão severos impactos na produção agrícola das áreas tropicais e temperadas, mas, embora sabido, ainda não havia sido adequadamente dimensionado.

Um recente estudo [Climatic Changes Lead to Declining Winter Chill for Fruit and Nut Trees in California during 1950–2099] da University of California, Davis e da University of Washington avaliou os impactos potenciais na Califórnia. A primeira conclusão foi de que as baixas temperaturas das ondas de friagem de inverno, essenciais para diversas frutas produzidas no estado, já foram reduzidas em 30% no período de 1950 até 2000.

O estado da Califórnia, em 2007, obteve uma produção agrícola estimada em US$ 7,8 bilhoes.

Usando informações do quarto relatório do IPCC (Intergovernmental Panel on Climate Change, 2007, os pesquisadores estimaram que, até meados do século 21, as ondas de friagem de inverno devem ser reduzidas em 60%, atingindo 80% ao final do século.

Estas condições inviabilizariam a produção de maçãs, cerejas, peras, nozes, pistachos, pêssegos, damascos, ameixas e cerejas.

Os pesquisadores destacam a importância do desenvolvimento de novas variedades que possam se adaptar às novas condições climáticas mas, ao mesmo tempo, reconhecem que isto, possivelmente, não ocorrerá a tempo.

A mesma ameaça está presente no Brasil e em vários outros países da América do Sul, o que pode significar uma grande redução na produção agrícola e uma significativa ameaça à segurança alimentar.

O estudo “Climatic Changes Lead to Declining Winter Chill for Fruit and Nut Trees in California during 1950–2099” foi publicado na Plos ONE e está disponível para acesso integral no formato HTML. Para acessar o artigo clique aqui.

Para outras informações transcrevemos, abaixo, o abstract:

Climatic Changes Lead to Declining Winter Chill for Fruit and Nut Trees in California during 1950–2099
Eike Luedeling1,2*, Minghua Zhang1*, Evan H. Girvetz3
1 Department of Land, Air and Water Resources, University of California Davis, Davis, California, United States of America, 2 Department of Plant Sciences, University of California Davis, Davis, California, United States of America, 3 College of Forest Resources, University of Washington, Seattle, Washington, United States of America

Abstract

Background
Winter chill is one of the defining characteristics of a location’s suitability for the production of many tree crops. We mapped and investigated observed historic and projected future changes in winter chill in California, quantified with two different chilling models (Chilling Hours, Dynamic Model).

Methodology/Principal Findings
Based on hourly and daily temperature records, winter chill was modeled for two past temperature scenarios (1950 and 2000), and 18 future scenarios (average conditions during 2041–2060 and 2080–2099 under each of the B1, A1B and A2 IPCC greenhouse gas emissions scenarios, for the CSIRO-MK3, HadCM3 and MIROC climate models). For each scenario, 100 replications of the yearly temperature record were produced, using a stochastic weather generator. We then introduced and mapped a novel climatic statistic, “safe winter chill”, the 10% quantile of the resulting chilling distributions. This metric can be interpreted as the amount of chilling that growers can safely expect under each scenario. Winter chill declined substantially for all emissions scenarios, with the area of safe winter chill for many tree species or cultivars decreasing 50–75% by mid-21st century, and 90–100% by late century.

Conclusions/Significance
Both chilling models consistently projected climatic conditions by the middle to end of the 21st century that will no longer support some of the main tree crops currently grown in California, with the Chilling Hours Model projecting greater changes than the Dynamic Model. The tree crop industry in California will likely need to develop agricultural adaptation measures (e.g. low-chill varieties and dormancy-breaking chemicals) to cope with these projected changes. For some crops, production might no longer be possible.

Citation: Luedeling E, Zhang M, Girvetz EH (2009) Climatic Changes Lead to Declining Winter Chill for Fruit and Nut Trees in California during 1950–2099. PLoS ONE 4(7): e6166. doi:10.1371/journal.pone.0006166

Editor: Samuel P. Hazen, University of Massachusetts Amherst, United States of America
Received: April 16, 2009; Accepted: June 3, 2009; Published: July 22, 2009

Copyright: © 2009 Luedeling et al. This is an open-access article distributed under the terms of the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: This work was funded by the California Department of Food and Agriculture (CDFA; award # SC107008). EHG was supported by a generous donation from Abby Leigh to The Nature Conservancy. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

* E-mail: eluedeling{at}ucdavis.edu (EL); mhzhang{at}ucdavis.edu (MZ)

[t]

EcoDebate, 03/08/2009

Inclusão na lista de distribuição do Boletim Diário do Portal EcoDebate
Caso queira ser incluído(a) na lista de distribuição de nosso boletim diário, basta que envie um e-mail para newsletter_ecodebate-subscribe@googlegroups.com . O seu e-mail será incluído e você receberá uma mensagem solicitando que confirme a inscrição.