Hasil untuk "America"

M. Smith, R. Saunders, Leigh Stuckhardt et al.

E. Berbari, S. Kanj, Todd J. Kowalski et al.

John H. Aldrich

M. McPherson, L. Smith-Lovin, Matthew E. Brashears

P. Mote, A. Hamlet, M. Clark et al.

B. Rosenberg, Dennis Wong

B. Cosin, S. Bowles, H. Gintis

I. Stewart, D. Cayan, M. Dettinger

T. Reardon, C. Timmer, C. Barrett et al.

M. Zuckerman, S. Eysenck, H. Eysenck

R. Katz

This chapter examines the future of American global leadership through the lens of its domestic political institutions. It finds that the United States faces growing troubles at home. At the same time, its vibrant economy, strong alliances relationships, and its unmatched military, all reflections of the U.S. domestic political system, will continue to provide a significant source of strategic advantage for the United States over its autocratic competitors in the years to come. The international security environment is becoming more competitive, and the United States does not exercise the unchallenged primacy it enjoyed in the 1990s. We have returned to an era of great power rivalry. But, there is no doubt that the United States remains the world’s leading power.

J. Enders

P. Bourke

S. Howell, S. Webb

F. Cardoso

Guillermo A. Calvo, L. Leiderman, Carmen Reinhart

The characteristics of recent capital inflows into Latin America are discussed. It is argued that these inflows are partly explained by conditions outside the region, like the recession in the United States and lower international interest rates. The importance of external factors suggests that a reversal of those conditions may lead to a future capital outflow, increasing the macroeconomic vulnerability of Latin American economies. Policy options, it is argued, are limited.

M. Fiorina, S. Abrams, J. Pope

R. Reis, J. Albert, F. D. Dario et al.

The freshwater and marine fish faunas of South America are the most diverse on Earth, with current species richness estimates standing above 9100 species. In addition, over the last decade at least 100 species were described every year. There are currently about 5160 freshwater fish species, and the estimate for the freshwater fish fauna alone points to a final diversity between 8000 and 9000 species. South America also has c. 4000 species of marine fishes. The mega-diverse fish faunas of South America evolved over a period of >100 million years, with most lineages tracing origins to Gondwana and the adjacent Tethys Sea. This high diversity was in part maintained by escaping the mass extinctions and biotic turnovers associated with Cenozoic climate cooling, the formation of boreal and temperate zones at high latitudes and aridification in many places at equatorial latitudes. The fresh waters of the continent are divided into 13 basin complexes, large basins consolidated as a single unit plus historically connected adjacent coastal drainages, and smaller coastal basins grouped together on the basis of biogeographic criteria. Species diversity, endemism, noteworthy groups and state of knowledge of each basin complex are described. Marine habitats around South America, both coastal and oceanic, are also described in terms of fish diversity, endemism and state of knowledge. Because of extensive land use changes, hydroelectric damming, water divergence for irrigation, urbanization, sedimentation and overfishing 4-10% of all fish species in South America face some degree of extinction risk, mainly due to habitat loss and degradation. These figures suggest that the conservation status of South American freshwater fish faunas is better than in most other regions of the world, but the marine fishes are as threatened as elsewhere. Conserving the remarkable aquatic habitats and fishes of South America is a growing challenge in face of the rapid anthropogenic changes of the 21st century, and deserves attention from conservationists and policy makers.

T. Barlam, S. Cosgrove, L. Abbo et al.

Yuchang Jiang, Anton Raichuk, Xiaoye Tong et al.

Monitoring tree crop expansion is vital for zero-deforestation policies like the European Union's Regulation on Deforestation-free Products (EUDR). However, these efforts are hindered by a lack of highresolution data distinguishing diverse agricultural systems from forests. Here, we present the first 10m-resolution tree crop map for South America, generated using a multi-modal, spatio-temporal deep learning model trained on Sentinel-1 and Sentinel-2 satellite imagery time series. The map identifies approximately 11 million hectares of tree crops, 23% of which is linked to 2000-2020 forest cover loss. Critically, our analysis reveals that existing regulatory maps supporting the EUDR often classify established agriculture, particularly smallholder agroforestry, as "forest". This discrepancy risks false deforestation alerts and unfair penalties for small-scale farmers. Our work mitigates this risk by providing a high-resolution baseline, supporting conservation policies that are effective, inclusive, and equitable.