Normally investing at least 80% of assets in environmental debt securities of all types and repurchase agreements for those securities. Environmental debt securities include debt securities of issuers that develop or provide products or services that seek to provide environmental solutions and/or support efforts to reduce their own environmental footprint, and debt securities that support environmental projects. Environmental debt securities include issuers, including sovereign or government-related issuers, (i) contained in the Bloomberg MSCI Global Green Bond USD Index (Hedged USD) and/or (ii) that have an above average environmental score as categorized by MSCI or are rated low risk or better by Sustainalytics. Normally investing primarily in investment-grade debt securities. Managing the fund with reference to the overall interest rate risk of the Bloomberg U.S. Aggregate Bond Index. Investing in domestic and foreign issuers. Allocating assets across different market sectors and maturities. Investing up to 20% of assets in lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds). Hedging the fund's foreign currency exposures utilizing forward foreign currency exchange contracts. Analyzing the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities to select investments. Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest rate, total return, and credit default), options, and futures contracts - and forward-settling securities, to adjust the fund's risk exposure. Employing sustainable investing exclusion criteria to avoid investments in issuers that are directly engaged in, and/or derive significant revenue from, certain industries. Please see "Fund Basics - Investment Details - Sustainable Investing Exclusions" for additional information.